Method for reporting channel state information in wireless communication system and apparatus for the same

ABSTRACT

A method of reporting, by a user equipment (UE), channel state information (CSI) in a wireless communication system, includes: receiving, by the UE and from a base station (BS), downlink control information (DCI) related to an aperiodic CSI report that is to be performed by the UE in a slot n; determining, by the UE, a value n CQI_ref  based on a number of symbols Z′ related to a time for computing the CSI; determining, by the UE, a CSI reference resource as being a slot n−n CQI_ref  in a time domain that is to be used for the aperiodic CSI report; and transmitting, by the UE and to the BS, the aperiodic CSI report in the slot n, based on the CSI reference resource being slot n−n CQI_ref . The CSI may be calculated by using the most recent A CSI-RS, and thereby the most recent CSI may be reported.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/200,008, filed on Nov. 26, 2018, now allowed, which claims thebenefit of U.S. Provisional Application No. 62/590,399, filed on Nov.24, 2017, U.S. Provisional Application No. 62/621,003, filed on Jan. 23,2018, U.S. Provisional Application No. 62/615,902, filed on Jan. 10,2018, U.S. Provisional Application No. 62/630,224, filed on Feb. 13,2018 and KR Application No. 10-2018-0040478, filed on Apr. 6, 2018. Thedisclosures of the prior applications are incorporated by reference intheir entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to wireless communication and, moreparticularly, to a method for reporting Channel State Information (CSI)and an apparatus for supporting the method.

Related Art

Mobile communication systems have been generally developed to providevoice services while guaranteeing user mobility. Such mobilecommunication systems have gradually expanded their coverage from voiceservices through data services up to high-speed data services. However,as current mobile communication systems suffer resource shortages andusers demand even higher-speed services, development of more advancedmobile communication systems is needed.

The requirements of the next-generation mobile communication system mayinclude supporting huge data traffic, a remarkable increase in thetransfer rate of each user, the accommodation of a significantlyincreased number of connection devices, very low end-to-end latency, andhigh energy efficiency. To this end, various techniques, such as smallcell enhancement, dual connectivity, massive multiple input multipleoutput (MIMO), in-band full duplex, non-orthogonal multiple access(NOMA), supporting super-wide band, and device networking, have beenresearched.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method fordetermining a CSI reference resource related to CSI reporting.

Technical objects to be achieved by the present invention are notlimited to those described above, and other technical objects notmentioned above may also be clearly understood from the descriptionsgiven below by those skilled in the art to which the present inventionbelongs.

The present document provides a method for transmitting and receiving aCSI-RS in a wireless communication system.

More specifically, a method performed by a user equipment (UE) comprisesreceiving, by the UE and from a base station (BS), downlink controlinformation (DCI) related to an aperiodic CSI report that is to beperformed by the UE in a slot n; determining, by the UE, a valuen_(CQI_ref) based on a number of symbols Z′ related to a time forcomputing the CSI; determining, by the UE, a CSI reference resource asbeing a slot n−n_(CQI_ref) in a time domain that is to be used for theaperiodic CSI report; and transmitting, by the UE and to the BS, theaperiodic CSI report in the slot n, based on the CSI reference resourcebeing slot n−n_(CQI_ref).

Also, according to the present invention, the n_(CQI_ref) is a smallestvalue greater than or equal to └Z′/N_(symb) ^(slot) ┘ such that the slotn−n_(CQI_ref) satisfies a valid downlink slot criteria, and wherein └·┘is a floor function and N_(symb) ^(slot) is a number of symbols in oneslot.

Also, according to the present invention, the valid downlink slotcriteria is based at least on (i) the number of symbols Z′ related tothe time for computing the CSI and (ii) a DCI processing time.

Also, according to the present invention, N_(symb) ^(slot) is equal to14 symbols in a slot.

Also, the method according to the present invention further comprisesreceiving, from the BS, an aperiodic reference signal (CSI-RS) in theCSI reference resource, slot n−n_(CQI_ref); determining the CSI based onthe aperiodic CSI-RS; and generating the aperiodic CSI report based onthe CSI.

Also, the method according to the present invention further comprisesdetermining the number of symbols Z′ related to the time for computingthe CSI based on a CSI complexity and a subcarrier spacing.

Also, according to the present invention, the number of symbols Z′ doesnot include a DCI processing time.

Also, according to the present invention, determining the valuen_(CQI_ref) based on the number of symbols Z′ related to the time forcomputing the CSI comprises: determining the value n_(CQI_ref) based onthe number of symbols Z′ related to the time for computing the CSI, andfurther based on a number of symbols in one slot.

Also, according to the present invention, receiving the DCI comprises:receiving the DCI in a slot other than the slot n in which the aperiodicCSI report is to be performed.

Also, according to the present invention, based on the value n_(CQI_ref)being equal to zero, the aperiodic CSI report is performed in a sameslot as receiving the DCI.

Also, a user equipment (UE) configured to report channel stateinformation (CSI) in a wireless communication system, the UE comprising:a radio frequency (RF) module configured to transmit and receive radiosignals; at least one processor; and at least one computer memoryoperably connectable to the at least one processor and storinginstructions that, when executed, cause the at least one processor toperform operations comprising: receiving, via the RF module and from abase station (BS), downlink control information (DCI) related to anaperiodic CSI report that is to be performed by the UE in a slot n;determining, by the UE, a value n_(CQI_ref) based on a number of symbolsZ′ related to a time for computing the CSI; determining, by the UE, aCSI reference resource as being a slot n−n_(CQI_ref) in a time domainthat is to be used for the aperiodic CSI report; and transmitting, viathe RF module and to the BS, the aperiodic CSI report in the slot n,based on the CSI reference resource being slot n−n_(CQI_ref).

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included herein as a part ofdetailed descriptions to help understanding the present invention,provide embodiments of the present invention and describe technicalfeatures of the present invention with detailed descriptions below.

FIG. 1 illustrates one example of the overall system structure of an NRto which a method proposed by the present specification may be applied.

FIG. 2 illustrates a relationship between an uplink frame and a downlinkframe in a wireless communication system to which a method proposed bythe present specification may be applied.

FIG. 3 illustrates one example of a resource grid supported by awireless communication system to which a method proposed by the presentspecification may be applied.

FIG. 4 illustrates one example of a self-contained subframe structure towhich a method proposed by the present specification may be applied.

FIG. 5 illustrates a transceiver unit model in a wireless communicationsystem to which the present invention may be applied.

FIG. 6 is a flow diagram illustrating one example of a CSI-relatedprocedure.

FIG. 7 illustrates one example of the timing at which a periodic CSI-RSis received.

FIGS. 8 and 9 illustrate another example of the timing at which a periodCSI-RS is received.

FIG. 10 illustrates one example of a method for measuring CSI by usingan AP CSI-RS.

FIG. 11 illustrates one example of another method for measuring CSI byusing an AP CSI-RS.

FIG. 12 illustrates one example of an A-CSI report trigger for singleCSI proposed by the present specification.

FIG. 13 illustrates one example of an A-CSI report trigger for singleCSI having a periodic CSI-RS proposed by the present specification.

FIGS. 14 and 15 illustrate examples of a method for determining a timeoffset of a CSI reference resource proposed by the presentspecification.

FIG. 16 illustrates one example of an A-CSI report trigger for singleCSI having an aperiodic CSI-RS proposed by the present specification.

FIG. 17 is a flow diagram illustrating one example of a method foroperating a UE which performs CSI reporting proposed by the presentspecification.

FIG. 18 is a flow diagram illustrating one example of a method foroperating an eNB which receives a CSI report proposed by the presentspecification.

FIG. 19 illustrates one example of a method for implementing then_(CQI_REF) value proposed by the present specification.

FIG. 20 illustrates a block diagram of a wireless communication deviceto which methods proposed by the present specification may be applied.

FIG. 21 illustrates a block diagram of a communication device accordingto one embodiment of the present invention.

FIG. 22 illustrates one example of an RF module of a wirelesscommunication device to which a method proposed by the presentspecification may be applied.

FIG. 23 illustrates another example of an RF module of a wirelesscommunication device to which a method proposed by the presentspecification may be applied.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

In what follows, preferred embodiments of the present invention will bedescribed in detail with reference to appended drawings. Detaileddescriptions to be disclosed below with reference to the appendeddrawings are intended to describe illustrative embodiments of thepresent invention but are not intended to represent the sole embodimentof the present invention. Detailed descriptions below include specificdetails to provide complete understanding of the present invention.However, it should be understood by those skilled in the art that thepresent invention may be embodied without the specific details to beintroduced.

In some cases, to avoid obscuring the gist of the present invention,well-known structures and devices may be omitted or may be depicted inthe form of a block diagram with respect to core functions of eachstructure and device.

A base station in this document is regarded as a terminal node of anetwork, which performs communication directly with a UE. In thisdocument, particular operations regarded to be performed by the basestation may be performed by an upper node of the base station dependingon situations. In other words, it is apparent that in a networkconsisting of a plurality of network nodes including a base station,various operations performed for communication with a UE can beperformed by the base station or by network nodes other than the basestation. The term Base Station (BS) may be replaced with a term such asfixed station, Node B, evolved-NodeB (eNB), Base Transceiver System(BTS), Access Point (AP), or general NB (gNB). Also, a terminal can befixed or mobile; and the term may be replaced with a term such as UserEquipment (UE), Mobile Station (MS), User Terminal (UT), MobileSubscriber Station (MSS), Subscriber Station (SS), Advanced MobileStation (AMS), Wireless Terminal (WT), Machine-Type Communication (MTC)device, Machine-to-Machine (M2M) device, or Device-to-Device (D2D)device.

In what follows, downlink (DL) refers to communication from a basestation to a terminal, while uplink (UL) refers to communication from aterminal to a base station. In downlink transmission, a transmitter maybe part of the base station, and a receiver may be part of the terminal.Similarly, in uplink transmission, a transmitter may be part of theterminal, and a receiver may be part of the base station.

Specific terms used in the following descriptions are introduced to helpunderstanding the present invention, and the specific terms may be usedin different ways as long as it does not leave the technical scope ofthe present invention.

The technology described below may be used for various types of wirelessaccess systems based on Code Division Multiple Access (CDMA), FrequencyDivision Multiple Access (FDMA), Time Division Multiple Access (TDMA),Orthogonal Frequency Division Multiple Access (OFDMA), Single CarrierFrequency Division Multiple Access (SC-FDMA), or Non-Orthogonal MultipleAccess (NOMA). CDMA may be implemented by such radio technology asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented by such radio technology as Global System for Mobilecommunications (GSM), General Packet Radio Service (GPRS), or EnhancedData rates for GSM Evolution (EDGE). OFDMA may be implemented by suchradio technology as the IEEE 802.11 (Wi-Fi), the IEEE 802.16 (WiMAX),the IEEE 802-20, or Evolved UTRA (E-UTRA). UTRA is part of the UniversalMobile Telecommunications System (UMTS). The 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE) is part of the Evolved UMTS(E-UMTS) which uses the E-UTRA, employing OFDMA for downlink and SC-FDMAfor uplink transmission. The LTE-A (Advanced) is an evolved version ofthe 3GPP LTE system.

The 5G NR defines enhanced Mobile Broadband (eMBB), massive Machine TypeCommunication (mMTC), Ultra-Reliable and Low Latency Communications(URLLC), and vehicle-to-everything (V2X) depending on usage scenarios.

And the 5G NR standard is divided into standalone (SA) andnon-standalone (NSA) modes according to co-existence between the NRsystem and the LTE system.

And the 5G NR supports various subcarrier spacing and supports CP-OFDMfor downlink transmission while CP-OFDM and DFT-s-OFDM (SC-OFDM) foruplink transmission.

The embodiments of the present invention may be supported by standarddocuments disclosed for at least one of wireless access systems such asthe IEEE 802, 3GPP, and 3GPP2. In other words, those steps or portionsamong embodiments of the present invention not described to clearlyillustrate the technical principles of the present invention may bebacked up by the aforementioned documents. Also, all of the termsdisclosed in the present document may be described by the aforementionedstandard documents.

For the purpose of clarity, descriptions are given mainly with respectto the 3GPP LTE/LTE-A, but the technical features of the presentinvention are not limited to the specific system.

Definition of Terms

eLTE eNB: An eLTE eNB is an evolution of an eNB that supports aconnection for an EPC and an NGC.

gNB: A node for supporting NR in addition to a connection with an NGC

New RAN: A radio access network that supports NR or E-UTRA or interactswith an NGC

Network slice: A network slice is a network defined by an operator so asto provide a solution optimized for a specific market scenario thatrequires a specific requirement together with an inter-terminal range.

Network function: A network function is a logical node in a networkinfra that has a well-defined external interface and a well-definedfunctional operation.

NG-C: A control plane interface used for NG2 reference point between newRAN and an NGC

NG-U: A user plane interface used for NG3 reference point between newRAN and an NGC

Non-standalone NR: A deployment configuration in which a gNB requires anLTE eNB as an anchor for a control plane connection to an EPC orrequires an eLTE eNB as an anchor for a control plane connection to anNGC

Non-standalone E-UTRA: A deployment configuration an eLTE eNB requires agNB as an anchor for a control plane connection to an NGC.

User plane gateway: A terminal point of NG-U interface

Numerology: corresponds to one subcarrier spacing in the frequencydomain. Different numerology may be defined by scaling referencesubcarrier spacing by an integer N.

NR: NR Radio Access or New Radio

General System

FIG. 1 is a diagram illustrating an example of an overall structure of anew radio (NR) system to which a method proposed by the presentdisclosure may be implemented.

Referring to FIG. 1, an NG-RAN is composed of gNBs that provide an NG-RAuser plane (new AS sublayer/PDCP/RLC/MAC/PHY) and a control plane (RRC)protocol terminal for a UE (User Equipment).

The gNBs are connected to each other via an Xn interface.

The gNBs are also connected to an NGC via an NG interface.

More specifically, the gNBs are connected to a Access and MobilityManagement Function (AMF) via an N2 interface and a User Plane Function(UPF) via an N3 interface.

NR (New Rat) Numerology and Frame Structure

In the NR system, multiple numerologies may be supported. Thenumerologies may be defined by subcarrier spacing and a CP (CyclicPrefix) overhead. Spacing between the plurality of subcarriers may bederived by scaling basic subcarrier spacing into an integer N (or μ). Inaddition, although a very low subcarrier spacing is assumed not to beused at a very high subcarrier frequency, a numerology to be used may beselected independent of a frequency band.

In addition, in the NR system, a variety of frame structures accordingto the multiple numerologies may be supported.

Hereinafter, an Orthogonal Frequency Division Multiplexing (OFDM)numerology and a frame structure, which may be considered in the NRsystem, will be described.

A plurality of OFDM numerologies supported in the NR system may bedefined as in Table 1.

TABLE 1 μ Δf = 2^(μ) · 15 [kHz] Cyclic prefix 0 15 Normal 1 30 Normal 260 Normal, Extended 3 120 Normal 4 240 Normal 5 480 Normal

Regarding a frame structure in the NR system, a size of various fieldsin the time domain is expressed as a multiple of a time unit ofT_(s)=1/(Δf_(max)·N_(f)). In this case, Δf_(max)=480·10³, andN_(f)=4096. DL and UL transmission is configured as a radio frame havinga section of T_(f)=(Δf_(max)N_(f)/100)·T_(s)=10 ms. The radio frame iscomposed of ten subframes each having a section ofT_(sf)=(Δf_(max)N_(f)/1000)·T_(s)=1 ms. In this case, there may be a setof UL frames and a set of DL frames.

FIG. 2 illustrates a relationship between a UL frame and a DL frame in awireless communication system to which a method proposed by the presentdisclosure may be implemented.

As illustrated in FIG. 2, a UL frame number I from a User Equipment (UE)needs to be transmitted T_(TA)=N_(TA)T_(s) before the start of acorresponding DL frame in the UE.

Regarding the numerology μ, slots are numbered in ascending order ofn_(s) ^(μ)∈{0, . . . , N_(subframe) ^(slots,μ)−1} in a subframe, and inascending order of n_(s,f) ^(μ)∈{0, . . . , N_(frame) ^(slots,μ)−1} in aradio frame. One slot is composed of continuous OFDM symbols of N_(symb)^(μ), and N_(symb) ^(μ) is determined depending on a numerology in useand slot configuration. The start of slots n_(s) ^(μ) in a subframe istemporally aligned with the start of OFDM symbols n_(s) ^(μ)N_(symb)^(μ) in the same subframe.

Not all UEs are able to transmit and receive at the same time, and thismeans that not all OFDM symbols in a DL slot or an UL slot are availableto be used.

Table 2 shows the number of OFDM symbols per slot for a normal CP in thenumerology μ, and Table 3 shows the number of OFDM symbols per slot foran extended CP in the numerology μ.

TABLE 2 Slot configuration 0 1 μ N_(symb) ^(μ) N_(frame) ^(slots, μ)N_(subframe) ^(slots, μ) N_(symb) ^(μ) N_(frame) ^(slots, μ)N_(subframe) ^(slots, μ) 0 14 10 1 7 20 2 1 14 20 2 7 40 4 2 14 40 4 780 8 3 14 80 8 — — — 4 14 160 16 — — — 5 14 320 32 — — —

TABLE 3 Slot configuration 0 1 μ N_(symb) ^(μ) N_(frame) ^(slots, μ)N_(subframe) ^(slots, μ) N_(symb) ^(μ) N_(frame) ^(slots, μ)N_(subframe) ^(slots, μ) 0 12 10 1 6 20 2 1 12 20 2 6 40 4 2 12 40 4 680 8 3 12 80 8 — — — 4 12 160 16 — — — 5 12 320 32 — — —

NR Physical Resource

Regarding physical resources in the NR system, an antenna port, aresource grid, a resource element, a resource block, a carrier part,etc. may be considered.

Hereinafter, the above physical resources possible to be considered inthe NR system will be described in more detail.

First, regarding an antenna port, the antenna port is defined such thata channel over which a symbol on one antenna port is transmitted can beinferred from another channel over which a symbol on the same antennaport is transmitted. When large-scale properties of a channel receivedover which a symbol on one antenna port can be inferred from anotherchannel over which a symbol on another antenna port is transmitted, thetwo antenna ports may be in a QC/QCL (quasi co-located or quasico-location) relationship. Herein, the large-scale properties mayinclude at least one of delay spread, Doppler spread, Doppler shift,average gain, and average delay.

FIG. 3 illustrates an example of a resource grid supported in a wirelesscommunication system to which a method proposed by the presentdisclosure may be implemented.

Referring to FIG. 3, a resource grid is composed of N_(RB) ^(μ)N_(sc)^(RB) subcarriers in a frequency domain, each subframe composed of 14·2μOFDM symbols, but the present disclosure is not limited thereto.

In the NR system, a transmitted signal is described by one or moreresource grids, composed of N_(RB) ^(μ)N_(sc) ^(RB) subcarriers, and2^(μ)N_(symb) ^((μ)) OFDM symbols Herein, N_(RB) ^(μ)≤N_(RB) ^(max,μ).The above N_(RB) ^(max,μ) indicates the maximum transmission bandwidth,and it may change not just between numerologies, but between UL and DL.

In this case, as illustrated in FIG. 3, one resource grid may beconfigured for the numerology μ and an antenna port p.

Each element of the resource grid for the numerology μ and the antennaport p is indicated as a resource element, and may be uniquelyidentified by an index pair (k,l). Herein, k=0, . . . , N_(RB)^(μ)N_(sc) ^(RB)−1 is an index in the frequency domain, and l=0, . . . ,2^(μ)N_(symb) ^((μ))−1 indicates a location of a symbol in a subframe.To indicate a resource element in a slot, the index pair (k,l) is used.Herein, l=0, . . . , N_(symb) ^(μ)−1.

The resource element (k,l) for the numerology μ and the antenna port pcorresponds to a complex value a_(k,l) ^((p,μ)). When there is no riskof confusion or when a specific antenna port or numerology is specified,the indexes p and μ may be dropped and thereby the complex value maybecome a_(k,l) ^((p)) or a_(k,l) .

In addition, a physical resource block is defined as N_(sc) ^(RB)=12continuous subcarriers in the frequency domain. In the frequency domain,physical resource blocks may be numbered from 0 to N_(RB) ^(μ)−1. Atthis point, a relationship between the physical resource block numbern_(PRB) and the resource elements (k,l) may be given as in Equation 1.

$\begin{matrix}{n_{PRB} = \left\lfloor \frac{k}{N_{sc}^{RB}} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In addition, regarding a carrier part, a UE may be configured to receiveor transmit the carrier part using only a subset of a resource grid. Atthis point, a set of resource blocks which the UE is configured toreceive or transmit are numbered from 0 to N_(URB) ^(μ)−1 in thefrequency region.

Self-Contained Subframe Structure

FIG. 4 is a diagram illustrating an example of a self-contained subframestructure in a wireless communication system to which the presentdisclosure may be implemented.

In order to minimize data transmission latency in a TDD system, 5G newRAT considers a self-contained subframe structure as shown in FIG. 4.

In FIG. 4, a diagonal line area (symbol index 0) represents a UL controlarea, and a black area (symbol index 13) represents a UL control area. Anon0shade area may be used for DL data transmission or for UL datatransmission. This structure is characterized in that DL transmissionand UL transmission are performed sequentially in one subframe andtherefore transmission of DL data and reception of UL ACK/NACK may beperformed in the subframe. In conclusion, it is possible to reduce timefor retransmitting data upon occurrence of a data transmission error andthereby minimize a latency of final data transmission.

In this self-contained subframe structure, a time gap is necessary for abase station or a UE to switch from a transmission mode to a receptionmode or to switch from the reception mode to the transmission mode. Tothis end, some OFDM symbols at a point in time of switching from DL toUL in the self-contained subframe structure are configured as a guardperiod (GP).

Analog Beamforming

Since a wavelength is short in a Millimeter Wave (mmW) range, aplurality of antenna elements may be installed in the same size of area.That is, a wavelength in the frequency band 30 GHz is 1 cm, and thus, 64(8×8) antenna elements may be installed in two-dimensional arrangementwith a 0.5 lambda (that is, a wavelength) in 4×4 (4 by 4) cm panel.Therefore, in the mmW range, the coverage may be enhanced or athroughput may be increased by increasing a beamforming (BF) gain with aplurality of antenna elements.

In this case, in order to enable adjusting transmission power and phasefor each antenna element, if a transceiver unit (TXRU) is included,independent beamforming for each frequency resource is possible.However, it is not cost-efficient to install TXRU at each of about 100antenna elements. Thus, a method is considered in which a plurality ofantenna elements is mapped to one TXRU and a direction of beam isadjusted with an analog phase shifter. Such an analog BF method is ableto make only one beam direction over the entire frequency band, andthere is a disadvantage that frequency-selective BF is not allowed.

A hybrid BF may be considered which is an intermediate between digitalBF and analog BF, and which has B number of TXRU less than Q number ofantenna elements. In this case, although varying depending upon a methodof connecting B number of TXRU and Q number of antenna elements, beamdirections capable of being transmitted at the same time is restrictedto be less than B.

Hereinafter, typical examples of a method of connecting TXRU and antennaelements will be described with reference to drawings.

FIG. 5 is an example of a transceiver unit model in a wirelesscommunication system to which the present disclosure may be implemented.

A TXRU virtualization model represents a relationship between outputsignals from TXRUs and output signals from antenna elements. Dependingon a relationship between antenna elements and TXRUs, the TXRUvirtualization model may be classified as a TXRU virtualization modeloption-1: sub-array partition model, as shown in FIG. 5(a), or as a TXRUvirtualization model option-2: full-connection model.

Referring to FIG. 5(a), in the sub-array partition model, the antennaelements are divided into multiple antenna element groups, and each TXRUmay be connected to one of the multiple antenna element groups. In thiscase, the antenna elements are connected to only one TXRU.

Referring to FIG. 5(b), in the full-connection model, signals frommultiple TXRUs are combined and transmitted to a single antenna element(or arrangement of antenna elements). That is, this shows a method inwhich a TXRU is connected to all antenna elements. In this case, theantenna elements are connected to all the TXRUs.

In FIG. 5, q represents a transmitted signal vector of antenna elementshaving M number of co-polarized in one column. W represents a widebandTXRU virtualization weight vector, and W represents a phase vector to bemultiplied by an analog phase shifter. That is, a direction of analogbeamforming is decided by W. x represents a signal vector of M_TXRUnumber of TXRUs.

Herein, mapping of the antenna ports and TXRUs may be performed on thebasis of 1-to-1 or 1-to-many.

TXRU-to-element mapping In FIG. 5 is merely an example, and the presentdisclosure is not limited thereto and may be equivalently applied evento mapping of TXRUs and antenna elements which can be implemented in avariety of hardware forms.

Channel State Information (CSI) Feedback

In most cellular systems including an LTE system, a UE receives a pilotsignal (or a reference signal) for estimating a channel from a basestation, calculate channel state information (CSI), and reports the CSIto the base station.

The base station transmits a data signal based on the CSI informationfed back from the UE.

The CSI information fed back from the UE in the LTE system includeschannel quality information (CQI), a precoding matrix index (PMI), and arank indicator (RI).

CQI feedback is wireless channel quality information which is providedto the base station for a purpose (link adaptation purpose) of providinga guidance as to which modulation & coding scheme (MCS) to be appliedwhen the base station transmits data.

In the case where there is a high wireless quality of communicationbetween the base station and the UE, the UE may feed back a high CQIvalue and the base station may transmit data by applying a relativelyhigh modulation order and a low channel coding rate. In the oppositecase, the UE may feed back a low CQI value and the base station maytransmit data by applying a relatively low modulation order and a highchannel coding rate.

PMI feedback is preferred precoding matrix information which is providedto a base station in order to provide a guidance as to which MIMOprecoding scheme is to be applied when the base station has installedmultiple antennas.

A UE estimates a downlink MIMO channel between the base station and theUE from a pilot signal, and recommends, through PMI feedback, which MIMOprecoding is desired to be applied by the base station.

In the LTE system, only linear MIMO precoding capable of expressing PMIconfiguration in a matrix form is considered.

The base station and the UE share a codebook composed of a plurality ofprecoding matrixes, and each MIMO precoding matrix in the codebook has aunique index.

Accordingly, by feeding back an index corresponding to the mostpreferred MIMO precoding matrix in the codebook as PMI, the UE minimizesan amount of feedback information thereof.

A PMI value is not necessarily composed of one index. For example, inthe case where there are eight transmitter antenna ports in the LTEsystem, a final 8tx MIMO precoding matrix may be derived only when twoindexes (first PMI & second PMI) are combined.

RI feedback is information on the number of preferred transmissionlayers, the information which is provided to the base station in orderto provide a guidance as to the number of the UE's preferredtransmission layers when the base station and the UE have installedmultiple antennas to thereby enable multi-layer transmission throughspatial multiplexing.

The RI and the PMI are very closely correlated to each other. It isbecause the base station is able to know which precoding needs to beapplied to which layer depending on the number of transmission layers.

Regarding configuration of PMI/RM feedback, a PMI codebook may beconfigured with respect to single layer transmission and then PMI may bedefined for each layer and fed back, but this method has a disadvantagethat an amount of PMI/RI feedback information increases remarkably inaccordance with an increase in the number of transmission layers.

Accordingly, in the LTE system, a PMI codebook is defined depending onthe number of transmission layers. That is, for R-layer transmission, Nnumber of Nt×R matrixes are defined (herein, R represents the number oflayers, Nt represents the number of transmitter antenna ports, and Nrepresents the size of the codebook).

Accordingly, in LTE, a size of a PMI codebook is defined irrespective ofthe number of transmission layers. As a result, since PMI/RI is definedin this structure, the number of transmission layers (R) conforms to arank value of the precoding matrix (Nt×R matrix), and, for this reason,the term “rank indicator(RI)” is used.

Unlike PMI/RI in the LTE system, PMI/RI described in the presentdisclosure is not restricted to mean an index value of a precodingmatrix Nt×R and a rank value of the precoding matrix.

PMI described in the present disclosure indicates information on apreferred MINO precoder from among MIMO precoders capable of beingapplied by a transmitter, and a form of the precoder is not limited to alinear precoder which is able to be expressed in a matrix form, unlikein the LTE system. In addition, RI described in the present disclosuremeans wider than RO in LTE and includes feedback information indicatingthe number of preferred transmission layers.

The CSI information may be obtained in all system frequency domains orin some of the frequency domains. In particular, in a broad bandwidthsystem, it may be useful to obtain CSI information on some frequencydomains (e.g., subband) preferred by each UE and then feedback theobtained CSI information.

In the LTE system, CSI feedback is performed via an UL channel, and, ingeneral, periodic CSI feedback is performed via a physical uplinkcontrol channel (PUCCH) and aperiodic CSI feedback is performed viaphysical uplink shared channel (PUSCH) which is a UL data channel.

The aperiodic CSI feedback means temporarily transmitting a feedbackonly when a base station needs CSI feedback information, and the basestation triggers the CSI feedback via a DL control channel such as aPDCCH/ePDCCH.

In the LTE system, which information a UE needs to feedback in responseto triggering of CSI feedback is defined as a PUSCH CSI reporting mode,as shown in FIG. 8, and a PUSCH CSI reporting mode in which the UE needsto operate is informed for the UE in advance via a higher layer message.

Channel State Information (CSI)-Related Procedure

In the new radio (NR) system, a channel state information-referencesignal (CSI-RS) is used for time/frequency tracking, CSI computation,layer 1(L1)-reference signal received power (RSRP) computation, ormobility

Throughout the present disclosure, “A and/or B” may be interpreted asthe same as “including at least one of A or B”.

The CSI computation is related to CSI acquisition, and L1-RSRPcomputation is related to beam management (BM).

The CSI indicates all types of information indicative of a quality of aradio channel (or link) formed between a UE and an antenna port.

Hereinafter, operation of a UE with respect to the CSI-related procedurewill be described.

FIG. 6 is a flowchart illustrating an example of a CSI-relatedprocedure.

To perform one of the above purposes of a CSI-RS, a terminal (e.g., aUE) receives CSI related configuration information from a base station(e.g., a general node B (gNB)) through a radio resource control (RRC)signaling (S610).

The CSI-related configuration information may include at least one ofCSI interference management (IM) resource-related information, CSImeasurement configuration-related information, CSI resourceconfiguration-related information, CSI-RS resource-related information,or CSI report configuration-related information.

The CSIIM resource-related information may include CSI-IM resourceinformation, CSI-IM resource set information, etc.

The CSI-IM resource set is identified by a CSI-IM resource set ID(identifier), and one resource set includes at least one CSI-IMresource.

Each CSI-IM resource is identified by a CSI-IM resource ID.

The CSI resource configuration-related information defines a groupincluding at least one of a non-zero power (NZP) CSI-RS resource set, aCSI-IM resource set, or a CSI-SSB resource set.

That is, the CSI resource configuration-related information includes aCSI-RS resource set list, and the CSI-RS resource set list may includeat least one of a NZP CSI-RS resource set list, a CSI-IM resource setlist, or a CSI-SSB resource set list.

The CSI resource configuration-related information may be expressed asCSI-REsourceConfig IE.

The CSI-RS resource set is identified by a CSI-RS resource set ID, andone resource set includes at least one CSI-RS resource.

Each CSI-RS resource is identified by a CSI-RS resource ID.

As shown in Table 4, parameters (e.g.: the BM-related parameterrepetition, and the tracking-related parameter trs-Info indicative of(or indicating) a purpose of a CSI-RS may be set for each NZP CSI-RSresource set.

Table 4 shows an example of NZP CSI-RS resource set IE.

TABLE 4 -- ASN1START -- TAG-NZP-CSI-RS-RESOURCESET-STARTNZP-CSI-RS-ResourceSet :: = SEQUENCE { nzp-CSI-ResourceSetIdNZP-CSI-RS-ResourceSetId, nzp-CSI-RS-Resources SEQUENCE (SIZE(1..maxNrofNZP-CSI-RS-ResourcesPerSet)) OF NZP-CSI-RS-ResourceId,repetition ENUMERATED { on, off } OPTIONAL, aperiodicTriggeringOffsetINTEGER(0..4) OPTIONAL, -- Need S trs-Info ENUMERATED {true} OPTIONAL,-- Need R ... } -- TAG-NZP-CSI-RS-RESOURCESET-STOP -- ASN1STOP

In Table 4, the parameter repetition is a parameter indicative ofwhether to repeatedly transmit the same beam, and indicates whetherrepetition is set to “ON” or “OFF” for each NZP CSI-RS resource set.

The term “transmission (Tx) beam” used in the present disclosure may beinterpreted as the same as a spatial domain transmission filter, and theterm “reception (Rx) beam” used in the present disclosure may beinterpreted as the same as a spatial domain reception filter.

For example, when the parameter repetition in Table 4 is set to “OFF”, aUE does not assume that a NZP CSI-RS resource(s) in a resource set istransmitted to the same DL spatial domain transmission filter and thesame Nrofports in all symbols.

In addition, the parameter repetition corresponding to a higher layerparameter corresponds to “CSI-RS-ResourceRep” of L1 parameter.

The CSI report configuration related information includes the parameterreportConfigType indicative of a time domain behavior and the parameterreportQuantity indicative of a CSI-related quantity to be reported.

The time domain behavior may be periodic, aperiodic, or semi-persistent.

In addition, the CSI report configuration-related information may berepresented as CSI-ReportConfig IE, and Table 5 shows an example of theCSI-ReportConfig IE.

TABLE 5 -- ASN1START -- TAG-CSI-RESOURCECONFIG-START CSI-ReportConfig::= SEQUENCE { reportConfigId CSI-ReportConfigId, carrier ServCellIndexOPTIONAL, -- Need S resourcesForChannelMeasurement CSI-ResourceConfigId,csi-IM-ResourcesForInterference CSI-ResourceConfigId OPTIONAL, -- Need Rnzp-CSI-RS-ResourcesForInterference CSI-ResourceConfigId OPTIONAL, --Need R reportConfigType CHOICE { periodic SEQUENCE { reportSlotConfigCSI-ReportPeriodicityAndOffset, pucch-CSI-ResourceList SEQUENCE (SIZE(1..maxNrofBWPs)) OF PUCCH-CSI-Resource }, semiPersistentOnPUCCHSEQUENCE { reportSlotConfig CSI-ReportPeriodicityAndOffset,pucch-CSI-ResourceList SEQUENCE (SIZE (1..maxNrofBWPs)) OFPUCCH-CSI-Resource }, semiPersistentOnPUSCH SEQUENCE { reportSlotConfigENUMERATED {sl5, sl10, sl20, sl40, sl80, sl160, sl320},reportSlotOffsetList SEQUENCE (SIZE (1.. maxNrofUL-Allocations)) OFINTEGER(0..32), p0alpha P0-PUSCH-AlphaSetId }, aperiodic SEQUENCE {reportSlotOffsetList SEQUENCE (SIZE (1..maxNrofUL-Allocations)) OFINTEGER(0..32) } }, reportQuantity CHOICE { none NULL, cri-RI-PMI-CQINULL, cri-RI-i1 NULL, cri-RI-i1-CQI SEQUENCE { pdsch-BundleSizeForCSIENUMERATED {n2, n4} OPTIONAL }, cri-RI-CQI NULL, cri-RSRP NULL,ssb-Index-RSRP NULL, cri-RI-LI-PMI-CQI NULL },

In addition, the UE measures CSI based on configuration informationrelated to the CSI (S620).

Measuring the CSI may include (1) receiving a CSI-RS by the UE (S621)and (2) computing CSI based on the received CSI-RS (S622).

A sequence for the CSI-RS is generated by Equation 2, and aninitialization value of a pseudo-random sequence C(i) is defined byEquation 3.

$\begin{matrix}{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack \\{c_{init} = {\left( {{2^{10}\left( {{N_{symb}^{slot}n_{s,f}^{\mu}} + l + 1} \right)\left( {{2n_{ID}} + 1} \right)} + n_{ID}} \right){mod}\; 2^{31}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In Equations 2 and 3, n_(s,f) ^(μ) is a slot number within a radioframe, and a pseudo-random sequence generator is initialized with Cintat the start of each OFDM symbol where n_(s,f) ^(μ) is the slot numberwithin a radio frame.

In addition, l indicates an OFDM symbol number in a slot, and n_(ID)indicates higher-layer parameter scramblingID.

In addition, regarding the CSI-RS, resource element (RE) mapping ofCSI-RS resources of the CSI-RS is performed in time and frequencydomains by higher layer parameter CSI-RS-ResourceMapping.

Table 6 shows an example of CSI-RS-ResourceMapping IE.

TABLE 6 -- ASN1START -- TAG-CSI-RS-RESOURCEMAPPING-STARTCSI-RS-ResourceMapping ::= SEQUENCE { frequencyDomainAllocation CHOICE {row1 BIT STRING (SIZE (4)), row2 BIT STRING (SIZE (12)), row4 BIT STRING(SIZE (3)), other BIT STRING (SIZE (6)) }, nrofPorts ENUMERATED{p1,p2,p4,p8,p12,p16,p24,p32}, firstOFDMSymbolInTimeDomain INTEGER(0..13), firstOFDMSymbolInTimeDomain2 INTEGER (2..12) OPTIONAL, -- NeedR cdm-Type ENUMERATED {noCDM, fd-CDM2, cdm4-FD2-TD2, cdm8-FD2- TD4},density CHOICE { dot5 ENUMERATED {evenPRBs, oddPRBs}, one NULL, threeNULL, spare NULL }, freqBand CSI-FrequencyOccupation, ... }

In Table 6, a density (D) indicates a density of CSI-RS resourcesmeasured in a RE/port/physical resource block (PRB), and nrofPortsindicates the number of antenna ports.

In addition, the UE reports the measured CSI to the base station (S630).

Herein, when a quantity of CSI-ReportConfig in Table 6 is set to“none(or No report)”, the UE may skip the reporting.

However, even when the quantity is set to “none(or No report)”, the UEmay report the measured CSI to the base station.

The case where the quantity is set to “none” is t when an aperiodic TRSis triggered or when repetition is set.

Herein, it may be defined such that reporting by the UE is omitted onlywhen repetition is set to “ON”.

To put it briefly, when repetition is set to “ON” and “OFF”, a CSIreport may indicate any one of “No report”, “SSB Resource Indicator(SSBRI) and L1-RSRP”, and “CSI-RS Resource Indicator (CRI) and L1-RSRP”.

Alternatively, it may be defined to transmit a CSI report indicative of“SSBRI and L1-RSRP” or “CRI and L1-RSRP” when repetition is set to“OFF”, it may be defined such that, and to transmit a CSI reportindicative of “No report”, “SSBRI and L1-RSRP”, or “CRI and L1-RSRP”when repetition is “ON”.

CSI Measurement and Reporting Procedure

The NR system supports more flexible and dynamic CSI measurement andreporting.

The CSI measurement may include receiving a CSI-RS, and acquiring CSI bycomputing the received CSI-RS.

As time domain behaviors of CSI measurement and reporting,aperiodic/semi-persistent/periodic channel measurement (CM) andinterference measurement (IM) are supported.

To configure CSI-IM, four port NZP CSI-RS RE patterns are used.

CSI-IM-based IMR of NR has a design similar to CSI-IM of LTE and isconfigured independent of ZP CSI-RS resources for PDSCH rate matching.

In addition, each port in the NZP CSI-RS-based IMR emulates aninterference layer having (a desirable channel and) a pre-coded NZPCSI-RS.

This is about intra-cell interference measurement of a multi-user case,and it primarily targets MU interference.

At each port of the configured NZP CSI-RS-based IMR, the base stationtransmits the pre-coded NZP CSI-RS to the UE.

The UE assumes a channel/interference layer for each port in a resourceset, and measures interference.

If there is no PMI or RI feedback for a channel, a plurality ofresources are configured in a set and the base station or networkindicates, through DCI, a subset of NZP CSI-RS resources forchannel/interference measurement.

Resource setting and resource setting configuration will be described inmore detail.

Resource Setting

Each CSI resource setting “CSI-ResourceConfig” includes configuration ofS≥1 CSI resource set (which is given by higher layer parameter“csi-RS-ResourceSetList”).

Herein, a CSI resource setting corresponds to CSI-RS-resourcesetlist.

Herein, S represents the number of configured CSI-RS resource sets.

Herein, configuration of S≥1 CSI resource set includes each CSI resourceset including CSI-RS resources (composed of NZP CSI-RS or CSI-IM), and aSS/PBCH block (SSB) resource used for L1-RSRP computation.

Each CSI resource setting is positioned at a DL bandwidth part (BWP)identified by higher layer parameter bwp-id.

In addition, all CSI resource settings linked to a CSI reporting settinghave the same DL BWP.

In a CSI resource setting included in CSI-ResourceConfig IE, a timedomain behavior of a CSI-RS resource may be indicated by higher layerparameter resourceType and may be configured to be aperiodic, periodic,or semi-persistent.

The number S of CSI-RS resource sets configured for periodic andsemi-persistent CSI resource settings is restricted to “1”.

A periodicity and a slot offset configured for periodic andsemi-persistent CSI resource settings are given from a numerology ofrelated DL BWP, just like being given by bwp-id.

When the UE is configured with a plurality of CSI-ResourceConfigincluding the same NZP CSI-RS resource ID, the same time domain behavioris configured for the CSI-ResourceConfig.

When the UE is configured with a plurality of CSI-ResourceConfig havingthe same CSI-IM resource ID, the same time domain behavior is configuredfor the CSI-ResourceConfig.

Then, one or more CSI resource settings for channel measurement (CM) andinterference measurement (IM) are configured through higher layersignaling.

-   -   A CSI-IM resource for interference measurement.    -   An NZP CSI-RS resource for interference measurement.    -   An NZP CSI-RS resource for channel measurement.

That is, a channel measurement resource (CMR) may be an NZP CSI-RS forCSI acquisition, and an interference measurement resource (IMR) may bean NZP CSI-RS for CSI-IM and for IM.

Herein, CSI-IM (or a ZP CSI-RS for IM) is primarily used for inter-cellinterference measurement.

In addition, an NZP CSI-RS for IM is primarily used for intra-cellinterference measurement from multi-user.

The UE may assume that a CSI-RS resource(s) and a CSI-IM/NZP CSI-RSresource(s) for interference measurement configured for one CSIreporting is “QCL-TypeD” for each resource.

Resource Setting Configuration

As described above, a resource setting may represent a resource setlist.

Regarding aperiodic CSI, each trigger state configured using higherlayer parameter “CSI-AperiodicTriggerState” is that eachCSI-ReportConfig is associated with one or multiple CSI-ReportConfiglinked to a periodic, semi-persistent, or aperiodic resource setting.

One reporting setting may be connected to three resource settings atmaximum.

-   -   When one resource setting is configured, a resource setting        (given by higher layer parameter resourcesForChannelMeasurement)        is about channel measurement for L1-RSRP computation.    -   When two resource settings are configured, the first resource        setting (given by higher layer parameter        resourcesForChannelMeasurement) is for channel measurement and        the second resource setting (given by        csi-IM-ResourcesForInterference or        nzp-CSI-RS-ResourcesForInterference) is for CSI-IM or for        interference measurement performed on an NZP CSI-RS.    -   When three resource settings are configured, the first resource        setting (given by resourcesForChannelMeasurement) is for channel        measurement, the second resource setting (given by        csi-IM-ResourcesForInterference) is for CSI-IM based        interference measurement, and the third resource setting (given        by nzp-CSI-RS-ResourcesForInterference) is for NZP CSI-RS based        interference measurement.

Regarding semi-persistent or periodic CSI, each CSI-ReportConfig islinked to a periodic or semi-persistent resource setting.

-   -   When one resource setting (given by        resourcesForChannelMeasurement) is configured, the resource        setting is about channel measurement for L1-RSRP computation.    -   When two resource settings are configured, the first resource        setting (given by resourcesForChannelMeasurement) is for channel        measurement, and the second resource setting (given by the        higher layer parameter “csi-IM-ResourcesForInterference”) is        used for interference measurement performed on CSI-IM.

CSI computation regarding CSI measurement will be described in moredetail.

If interference measurement is performed on CSI-IM, each CSI-RS resourcefor channel measurement is associated with a CSI-RS resource in acorresponding resource set by an order of CSI-RS resources and CSI-IMresources.

The number of CSI-RS resources for channel measurement is the same asthe number of CSI-IM resources.

In addition, when interference measurement is performed on an NZPCSI-RS, the UE is not expected to be configured with one or more NZPCSI-RS resources in an associated resource set within a resource settingfor channel measurement.

A UE configured with higher layer parameternzp-CSI-RS-ResourcesForInterference is not expected to be configuredwith 18 or more NZP CSI-RS ports in a NZP CSI-RS resource set.

For CSI measurement, the UE assumes the following.

-   -   Each NZP CSI-RS port configured for interference measurement        corresponds to an interference transmission layer.    -   Every interference transmission layer of NZP CSI-RS ports for        interference measurement considers an energy per resource        element (EPRE) ratio.    -   a different interference signal on a RE(s) of an NZP CSI-RS        resource for channel measurement, an NZP CSI-RS resource for        interference measurement, or a CSI-IM resource for interference        measurement.

A CSI reporting procedure will be described in more detail.

For CSI reporting, time and frequency resources available for an UE arecontrolled by a base station.

CSI may include at least one of channel quality indicator (CQI), aprecoding matrix indicator (PMI), a CSI-RS resource indicator (CRI), amSS/PBCH block resource indicator (SSBRI), a layer indicator (LI), a rankindicator (RI), or L1-RSRP.

Regarding the CQI, the PMI, the CRI, the SSBRI, the LI, the RI, and theL1-RSRP, the UE may be configured with N≥1 CSI-ReportConfig reportingsetting, M≥1 CSI-ResourceConfig resource setting, and a list of one ortwo trigger states (provided by aperiodicTriggerStateList andsemiPersistentOnPUSCH-TriggerStateList) by a higher layer.

In the aperiodicTriggerStateList, each trigger state includes a channeland a list of associated CSI-ReportConfigs selectively indicative ofResource set IDs for interference.

In the semiPersistentOnPUSCH-TriggerStateList, each trigger stateincludes one associated CSI-ReportConfig.

In addition, a time domain behavior of CSI reporting supports periodic,semi-persistent, and aperiodic CSI reporting.

Hereinafter, periodic, semi-persistent, and aperiodic CSI reporting willbe described.

The periodic CSI presorting is performed on a short PUCCH and a longPUCCH.

A periodicity and a slot offset of the periodic CSI reporting may beconfigured by RRC and refer to CSI-ReportConfig IE.

Then, SP CSI reporting is performed on a short PUCCH, a long PUCCH, or aPUSCH.

In the case of SP CSI on a short/long PUCCH, a periodicity and a slotoffset are configured by RRC, and CSI reporting to an additional MAC CEis activated/deactivated

In the case of SP CSI on a PUSCH, a periodicity of SP CSI reporting isconfigured by RRC, but a slot offset thereof is not configured by RRCand SP CSI reporting is activated/deactivated by DCI (format 0_1).

The first CSI reporting timing follows a PUSCH time domain allocationvalue indicated by DCI, and subsequent CSI reporting timing follows aperiodicity which is configured by RRC.

For SP CSI reporting on a PUSCH, a separated RNTI (SP-CSI C-RNTI) isused.

DCI format 0_1 may include a CSI request field and activate/deactivate aspecific configured SP-CSI trigger state.

In addition, SP CSI reporting is activated/deactivated identically orsimilarly to a mechanism having data transmission on a SPS PUSCH.

Next, aperiodic CSI reporting is performed on a PUSCH and triggered byDCI.

In the case of AP CSI having an AP CSI-RS, an AP CSI-RS timing isconfigured by RRC.

Herein, a timing of AP CSI reporting is dynamically controlled by DCI.

A reporting method (e.g., transmitting in order of RI, WB, PMI/CQI, andSB PMI/CQI) by which CSI is divided and reported in a plurality ofreporting instances, the method which is applied for PUCCH-based CSIreporting in LTE, is not applied in NR.

Instead, NR restricts configuring specific CSI reporting on a short/longPUCCH, and a CSI omission rule is defined.

Regarding an AP CSI reporting timing, PUSCH symbol/slot location isdynamically indicated by DCI. In addition, candidate slot offsets areconfigured by RRC.

Regarding CSI reporting, a slot offset(Y) is configured for eachreporting setting.

Regarding UL-SCH, a slot offset K2 is configured separately.

Two CSI latency classes (low latency class and high latency class) aredefined in terms of CSI computation complexity.

The low latency CSI is WB CSI that includes up to 4-ports Type-Icodebook or up to 4-ports non-PMI feedback CSI.

The high latency CSI is a CSI other than the low latency CSI.

Regarding a normal UE, (Z, Z′) is defined in a unit of OFDM symbols.

Z represents the minimum CSI processing time after receiving CSItriggering DCI and before performing CSI reporting.

Z′ represents the minimum CSI processing time after receiving CSI-RSabout a channel/interference and before performing CSI reporting

Additionally, the UE reports the number of CSI which can be calculatedat the same time.

A-CSI or AP CSI used in the present specification indicates aperiodicCSI which is the CSI reported aperiodically by the UE.

Also, CSI report or CSI reporting used in the present specification maybe regarded to have the same meaning.

To inform of UE capability for A-CSI computation or calculation time,the UE reports a set of supported Z values and CSI configuration whichmay be supported for each Z value to the eNB.

Here, Z is defined by the minimum required number of symbols for CSIcomputation for a given CSI configuration.

More specifically, Z refers to the minimum amount of time required forcalculation related to AP CSI processing, such as decoding time, channelmeasurement, CSI calculation, and TX preparation.

A CSI configuration includes information indicating wideband (WB) onlyCSI or sub-band (SB) and WB CSI; information about the maximum number ofCSI-RS ports; and information about type 1 codebook or type 2 codebook.

When the UE supports a plurality of numerology, the information aboutCSI may be reported for each numerology.

When an A-CSI report is triggered at slot n on the PUSCH, the UE dropsthe A-CSI report for the following cases:

-   -   A case where the time gap between the last symbol of the PDCCH        and the start symbol of the PUSCH in the slot n is smaller than        a reported value of Z with respect to a given CSI configuration        and    -   A case where an AP CSI-RS resource is transmitted from the slot        n, and the time gap between the last symbol of a CSI-RS resource        and the start symbol of the PUSCH is smaller than a reported        value of Z with respect to a given CSI configuration.

And those symbols between the Z symbols before the start symbol of thePUSCH and the start symbol of the PUSCH are not valid as (CSI) referenceresources.

In what follows, an A-CSI report trigger and a CSI report relatedthereto will be described.

When the eNB triggers an A-CSI report through downlink controlinformation (DCI) transmission in the slot n, the UE operates asfollows.

A-CSI is transmitted by the UE through the PUSCH allocated as a resourceby the DCI.

The transmission timing of the PUSCH is indicated by a specific field(which is defined as a Y value) of the DCI.

More specifically, the PUSCH is transmitted from the (n+Y)-th slot (slotn+Y) with reference to the slot n which corresponds to the trigger timeof the A-CSI report.

For example, when a DCI field for the Y value is defined by 2 bits, theY value for 00, 01, 10, and 11 is defined respectively by RRC signalingand more specifically, defined within a report setting defined throughRRC signaling.

The report setting may also be expressed by reporting setting orCSI-ReportConfig.

An A-CSI report trigger may trigger one or more specific reportsettings, and the value of 00, 01, 10, and 11 of the DCI field isdefined according to the Y value defined within the triggered reportsetting.

As described above, when the time gap or timing gap between the lastsymbol of the PDCCH and the start symbol of the PUSCH is smaller thanthe Z value corresponding to the CSI configuration of triggered A-CSI,the UE transmits the triggered A-CSI to the eNB without dropping orupdating the A-CSI.

Since the amount of time allocated for actual calculation is smallerthan the minimum amount of time Z required for calculation of the A-CSI,the UE is unable to calculate the A-CSI.

As a result, the UE does not drop or update triggered CSI.

When a Non-Zero Power (NZP) CSI-RS or Zero Power (ZP) CSI-RS used forchannel estimation or interference estimation of triggered A-CSI is anaperiodic CSI-RS, the UE estimates a channel or interference through oneshot measurement from the corresponding RS.

In other words, it indicates that the UE estimates a channel orinterference by using the corresponding RS (NZP CSI-RS or ZP CSI-RS)only.

At this time, if the time gap between the very last symbol of a CSI-RSresource and the start symbol of the PUSCH is smaller than the Z valuecorresponding to the CSI configuration of triggered A-CSI, in the sameway as the UE's operation described above, the UE transmits thecorresponding A-CSI to the eNB without dropping or updating thecorresponding A-CSI.

And when the UE calculates CSI, the UE does so by assuming reception ofdata for a specific frequency and/or time resource area, which is calleda CSI reference resource.

The CSI reference resource may be simply referred to as a referenceresource.

Since the UE starts CSI calculation from the CSI reference resourcetime, the UE may calculate CSI only when the amount of time as long as Zsymbols from the CSI reference resource time is secured.

Therefore, the reference resource time has to be defined at least beforez symbols (or z+1 symbols) with respect to the CSI report time.

To this end, when validity of a reference resource is checked, symbolsor slots before at least z symbols (or z+1 symbols) are determined to bevalid with respect to the CSI report time, but invalid, otherwise.

Here, the (CSI) reference resource is defined in units of slots.

Also, the slot whose number is less than or equal to n−n_(CQI_REF)(namely slot n−n_(CQI_REF)) is determined as the (CSI) referenceresources with reference to the slot for CSI reporting (for example,slot n).

The statement above, which says that ‘symbols or slots before at least zsymbols (or z+1 symbols) are determined to be valid with respect to theCSI report time, but invalid, otherwise’, may indicate that n_(CQI_REF)is configured by Eq. 4 below.

$\begin{matrix}{n_{{CQI}\_ {REF}} = {{{floor}{\mspace{11mu} \;}\left( \frac{z}{\begin{matrix}{{{The}{\mspace{11mu} \;}{number}\mspace{14mu} {of}\mspace{14mu} {OFDM}{\mspace{11mu} \;}{symbols}}\mspace{14mu}} \\{{{comprising}\mspace{14mu} {one}{\mspace{11mu} \;}{slot}}\;}\end{matrix}} \right)} + 1}} & \left\lbrack {{Eq}.\mspace{14mu} 4} \right\rbrack\end{matrix}$

In Eq. 4, floor discards digits after the decimal point and is denotedby a symbol └·┘.

The UE sets the most recent slot which satisfies the validity conditionfor a reference resource among slots whose number is less than or equalto n−n_(CQI_REF) as a reference resource.

Similarly, the UE may simply set the slot n−n_(CQI_REF) as the referenceresource.

And the time offset of the CSI reference resource may be determined onthe basis of the proposal 3 to be described later, and detaileddescriptions about how the time offset of the CSI reference resource isdetermined will be given by the proposal 3.

The A-CSI report trigger field included in the DCI may be interpreted asfollows.

When an eNB instructs a UE to perform an A-CSI trigger for a pluralityof report settings simultaneously, and a definition of the Y value isdifferent for each report setting, a problem occurs as described below,and a UE operation to solve the problem through various methods will bedescribed.

For example, suppose a report setting 1 is defined as Y={0, 1, 2, 3},and a report setting 2 is defined as Y={1, 2, 3, 4}.

In this case, an ambiguity occurs in which value the (2 bits) DCI fieldindicating the Y value has to be interpreted.

Therefore, to remove the ambiguity, it is proposed that the UE operatesaccording to the following methods.

(Method 1)

The UE newly generates Y′ as an intersection between two different Ysand interprets the DCI field according to the Y′ value.

In other words, in the example above, the intersection of two differentYs is {1, 2, 3}, and the UE interprets 00, 01, 10, and 11 of the DCIfield as 1, 2, 3, and 3, respectively.

If the intersection between two different Ys is {1}, the UE interprets00, 01, 10, and 11 as 1, 1, 1, and 1, respectively.

If the intersection between two different Ys is {1, 2}, the UEinterprets 00, 01, 10, and 11 as 1, 2, 2, and 2.

In the example above, when the number of elements belonging to theintersection between two different Ys is smaller than the states (forexample, 00, 01, 10, and 11) of the DCI field, the remaining states aredefined by repeating the last intersection value.

However, different from the definition above, the remaining states maybe defined as reserved.

(Method 2)

The UE interprets the DCI field according to the Y value defined in oneof a plurality of report settings.

For example, among a plurality of report settings, the UE interprets theDCI field by using the Y value for a report setting having a low reportsetting index.

Similarly, among a plurality of report setting, the UE interprets theDCI field by using the Y value for a report setting having a low indexfor a component carrier (CC).

The UE puts priorities between the report setting index and the CC indexand determines a Y value for a report setting by using the CC index.

If the CC index is the same, the UE may then determine the Y valueaccording to the report setting index.

Or as described above, the priority may be reversed (a high priority isset for the report setting index).

(Method 3)

The UE may expect that a plurality of report settings always have thesame Y value.

In other words, the eNB configures the report settings 1 and 2 to havethe same Y value through RRC signaling.

For example, the eNB may configure the report setting 1 by using Y={1,2, 3, 4} and the report setting 2 by using Y={1, 2, 3, 4}.

(Method 4)

The UE determines the time offset of aperiodic CSI reporting by usingthe larger value of two different Y values.

For example, the report setting 1 may be defined by Y1={0, 1, 2, 3}, andthe report setting 2 may be defined by Y2={1, 2, 3, 4}.

When the DCI field for Y (for example, 2 bits) is ‘00’, Y1=0, and Y2=1;and therefore, the Y value is determined by ‘1’ which is the larger ofthe two values.

When the DCI field for Y (for example, 2 bits) is ‘01’, Y1=1, and Y2=2;and therefore, the Y value is determined by ‘2’ which is the larger ofthe two values.

The Y value may be defined in the same way as above when the DCI fieldvalue is ‘10’ and ‘11’, and the Y value for the DCI field value of ‘10’and ‘11’ is determined as ‘3’ and ‘4’, respectively.

If three Y values are defined, the largest one among the three valuesmay be determined as a time offset by applying the same method asdescribed above.

As described above, the eNB may instruct the UE to perform an AP CSIreporting trigger through one DCI and determine the time offset ofaperiodic CSI reporting according to the methods described above(Methods 1 to 4) by using the Y values defined for the respective Ntriggered AP CSI reporting settings.

In addition, the eNB may indicate the data transmission time through thePUSCH while performing an AP CSI reporting trigger through the same DCIsimultaneously.

At this time, the data transmission time through the PUSCH is defined asa ‘K2’ value, and a plurality of candidate sets are set to the UEthrough upper layer signaling in advance.

One of the candidate sets is determined (or selected) as a final K2value through the DCI field (which is also called a ‘timing offsetfield’).

Also, the DCI field for selecting the K2 value and the DCI field forselecting the Y value are not defined by separate fields but are definedby the same DCI field.

When an AP CSI reporting trigger occurs, the UE uses the correspondingDCI field to select the Y value, and when scheduling of PUSCH data isoccurred, the corresponding DCI field is used to select the K2 value.

When PUSCH data scheduling occurs while an AP CSI reporting trigger isperformed simultaneously through the DCI, an ambiguity arises aboutwhether to define each value of the timing offset field as a candidateof the Y value or a candidate for the K2 value.

To solve the ambiguity, it is possible to directly extend and apply theaforementioned methods (Methods 1 to 4).

In other words, the proposed methods (Methods 1 to 4) above are relatedto how to define the value of the timing offset field when a pluralityof Y candidate sets are given, and Methods 1 to 4 may also be applied tothe K2 candidate set by treating the K2 candidate set as one Y candidateset.

For example, Method 4 may be extended and applied as described below.

The UE defines the timing offset field by using the larger of differentY and K2 values.

For example, suppose a report setting 1 is defined as Y1={0, 1, 2, 3},and a report setting 2 is defined as K2={3, 4, 5, 6}.

If the DCI field of the timing offset is ‘00’, Y1=0, Y2=1, and K2=3; andtherefore, the timing offset field is determined by the largest value‘3’.

If the DCI field is ‘01’, Y1=1, Y2=2, and K2=4; and therefore, thetiming offset field is determined by the largest value ‘4’.

The DCI field values for ‘10’ and ‘11’ may be determined in the samemanner, and in this case, the DCI field values for ‘10’ and ‘11’ aredetermined as ‘5’ and ‘6’, respectively.

The UE may multiplex PUSCH data and CSI in the slot (n+timing offset)with respect to the slot n which has received DCI according to anindicated DCI value and report (or transmit) the multiplexed data andCSI to the eNB simultaneously.

Now, other methods for interpreting the A-CSI report trigger-related DCIfield in addition to the aforementioned methods (Methods 1 to 4) will bedescribed.

(Method 5)

In another method, the UE constructs a union set by combining candidatesets of different Ys and K2 candidate sets and defines the value of an nbit timing offset DCI field as the values ranging from the largestelement to the 2n-th largest element of the union set.

The UE multiplexes PUSCH data and CSI in the slot (n+timing offset) withrespect to the slot n which has received DCI according to an indicatedDCI value and reports (or transmits) the multiplexed data and CSI to theeNB simultaneously.

(Method 6)

In yet another method, after constructing one set from candidate sets ofYs through the Methods 1 to 4, a union set is constructed by combiningone of the Y candidate sets and a candidate set of K2.

And the DCI field value of an n bit timing offset is defined by thevalues ranging from the largest element to the 2n-th largest element ofthe union set.

(Method 7)

Method 7 constructs one set from candidate sets of Ys through theMethods 1 to 4 and defines the i-th value of the DCI field of the timingoffset by using a sum of the i-th element of one of the Y candidate setsand the i-th element of the K2 candidate sets.

For example, when the Y candidate set is {1,2,3,4}, and the K2 candidateset is {5, 6, 7, 8}, the respective values of the 2-bit timing offsetDCI field for 00, 01, 10, and 11 may be defined by 1+5 (6), 2+6 (8), 3+7(10), and 4+8 (12).

(Method 8)

Method 8 constructs one set from candidate sets of Ys through theMethods 1 to 4 and defines the i-th value of the timing offset DCI fieldas a sum of the i-th element of the candidate set of Ys while ignoringthe candidate set of K2.

Next, a relaxation method for AP CSI calculation will be described.

The UE reports a Z value as defined below to the eNB by using one ofcapabilities of the UE for AP CSI calculation.

By assuming CSI only PUSCH (no HARQ ACK/NACK) for a given numerology andCSI complexity, Z is defined as the minimum required number of symbolsfor PDCCH detection/decoding time for receiving DCI triggering a CSIreport, channel estimation time, and CSI calculation time.

For low complexity CSI, one Z value for a given numerology is defined asshown in Table 7 below.

And for high complexity CSI, one Z value for a given numerology isdefined as shown in Table 7 below.

TABLE 7 CSI 15 kHz 30 kHz 60 kHz 120 kHz complexity Units SCS SCS SCSSCS Low Symbols Z_(1,1) Z_(1, 2) Z_(1, 3) Z_(1, 4) complexity CSI HighSymbols Z_(2, 1) Z_(2, 2) Z_(2, 3) Z_(2, 4) complexity CSI 1 HighSymbols Z_(N+1, 1) Z_(N+1, 2) Z_(N+1, 3) Z_(N+1, 4) complexity CSI 2

As described above, Z is defined as a sum of the amount of time requiredfor DCI decoding (which means decoding time of DCI holding AP CSItrigger information), the amount of time required for channelestimation, and the amount of time required for CSI calculation.

According to the complexity of CSI triggered with respect to the Zvalue, the eNB indicates a Y value (in other words, according to whetherit is low complexity CSI or high complexity CSI).

If it is assumed that DCI holding an AP CSI trigger (namely AP CSItriggering DCI) is transmitted to slot n, the UE reports thecorresponding CSI to the eNB at slot (n+timing offset Y).

If the time allocated to the UE for CSI calculation is insufficient forthe UE's capability for AP CSI calculation, the UE, instead of updating(or calculating) CSI, transmits the most recently reported CSI orarbitrary CSI (or predefined, specific CSI, for example, CQI=0, PMI=0,and RI=1) to the eNB.

FIG. 7 illustrates the aforementioned situation. In other words, FIG. 7illustrates timing at which a periodic CSI-RS is received.

More specifically, FIG. 7 illustrates a situation in which the mostrecent periodic (P) CSI-RS which has been received at or beforereference resource time exists within a T time period.

In FIG. 7, the UE measures CSI through a periodic CSI-RS (P CSI-RS), andit may be noticed that the P CSI-RS and the CSI reference resource existwithin the time T.

In this case, within the time T, the UE performs all of DCI decoding,channel estimation, and CSI calculation.

Therefore, the UE compares T and Z and if T<Z, does not calculate (orupdate) CSI but transmits the most recently reported CSI or arbitraryCSI.

If T>=Z, the UE calculates CSI on the basis of the periodic CSI-RS andreports the calculated CSI to the eNB.

FIGS. 8 and 9 illustrate another example of the timing at which a periodCSI-RS is received.

In other words, FIGS. 8 and 9 illustrate a situation in which the mostrecent P CSI-RS received at or before the reference resource time existsbefore the T period.

Or, FIGS. 8 and 9 illustrate a situation in which a P CSI-RS does notexist within the T period, but the P CSI-RS exists before the T period.

In other words, referring to FIGS. 8 and 9, the UE has already performedchannel measurement from a (periodic) CSI-RS before a CSI report triggeris occurred.

Therefore, in this case, the UE performs DCI decoding and CSIcalculation within the T period.

The UE compares T and Z-(channel estimation time) and if T<Z-(channelestimation time), does not calculate (or update) CSI but transmits themost recently reported CSI or arbitrary CSI to the eNB.

Here, the UE may report the channel estimation time to the eNB by usingseparate capability.

If T>=Z-(channel estimation time), the UE calculates CSI and reports thecalculated CSI to the eNB.

Here, Z-(channel estimation time) may be defined by a third variable Z′,and the UE may report Z and Z′ to the eNB, respectively.

FIG. 10 illustrates one example of a method for measuring CSI by usingan AP CSI-RS.

First, an AP CSI-RS is defined to exist always within the time period T.

In this case, within the time T, the UE performs all of DCI decoding,channel estimation, and CSI calculation.

Therefore, the UE compares T and Z and if T<Z, does not calculate (orupdate) CSI but transmits the most recently reported CSI or arbitraryCSI.

If T>=Z, the UE calculates CSI and reports the calculated CSI to theeNB.

FIG. 11 illustrates one example of another method for measuring CSI byusing an AP CSI-RS.

More specifically, FIG. 11 illustrates a situation in which an AP CSI-RSis transmitted long after the UE finishes decoding of DCI.

In this case, the UE has to perform all of DCI decoding, channelestimation, and CSI calculation within the time period T.

However, since an AP CSI-RS is transmitted long after DCI decoding isfinished, the UE is unable to perform channel measurement and CSIcalculation during the time period T until the DCI decoding is finishedand the AP CSI-RS is transmitted.

Therefore, the UE compares T and Z and if T<Z, does not calculate (orupdate) CSI but may transmit the most recently reported CSI or arbitraryCSI to the eNB; however, if T>=Z, the UE is unable to calculate CSI andthus unable to report CSI to the eNB.

Therefore, to make the method as shown in FIG. 11 effective, the eNB hasto transmit an AP CSI-RS within the DCI decoding time after the lastOFDM symbol of triggering DCI.

Or the eNB has to transmit an AP CSI-RS before Z-(decoding time) at thefirst OFDM symbol from which AP CSI is reported.

The UE may report the decoding time to the eNB through separatecapability.

Here, Z-(decoding time) may be defined as a third variable Z′, and theUE may report Z and Z′ to the eNB, respectively.

In other words, T′ between the time at which the AP CSI-RS used forchannel measurement or interference measurement is last received and thestart time at which CSI is reported is smaller than Z′, the UEdetermines that time for calculating CSI is not sufficient and does notcalculate CSI.

Therefore, the UE does not report valid CSI but reports a predefineddummy CSI value (for example, RI=1, PMI=1, and CQI=1) to the eNB.

Or if T′ between the last OFDM symbol on which the AP CSI-RS istransmitted and the first OFDM symbol on which the AP-CSI is reported issmaller than Z-(decoding time), the UE does not calculate (or update)CSI but transmits the most recently reported CSI or arbitrary CSI to theeNB.

And if T′>=Z-(decoding time), and T<Z, the UE does not calculate (orupdate) CSI but transmits the most recently reported CSI or arbitraryCSI.

If T′>=Z-(decoding time) and T>=Z, the UE calculates CSI and reports thecalculated CSI to the eNB.

The UE may report the decoding time to the eNB through separatecapability.

Differently from the proposals to be described later, if Z′ isintroduced, the Z in the proposals 2 and 3 may be replaced with the Z′.

As described above, the Z indicates the minimum required time for all ofthe calculations related to AP CSI processing such as DCI decoding time,channel measurement, CSI calculation, and TX preparation.

And the Z′ indicates the minimum required time for channel measurement,CSI calculation, and TX preparation.

Therefore, it may be preferable to set the time provided for the UE,spanning from the last reception time of the CSI-RS used for channelmeasurement or interference measurement to the start time at which theCSI is transmitted, with reference to the Z′ which does not includedecoding time.

The proposals 2 and 3 below may be limited (or restricted) to the casewhere CSI is reported within a short time period after the A CSI reporttriggering.

For example, the proposals 2 and 3 to be described later may be appliedonly to the case of a small Y value such as Y=0 (or Y=1).

If Y=0, it may be related to the operation for self-contained CSIfeedback which is operated in one slot, including CSI report triggering,channel measurement, and up to CSI reporting.

For the self-contained structure, the descriptions given above may bereferenced.

To this purpose, a reference resource is defined to be as close aspossible from slot n, and the UE is made to measure a channel by using aCSI-RS within a time period between CSI report triggering and CSIreporting.

Or even if Y is a non-zero, small value (for example, Y=1), since theeNB is intended to trigger CSI reporting and to receive a fresh (or new)CSI report within a short time period, a reference resource may bedefined to be as close as possible from slot n, and the eNB may be madeto perform channel measurement by using a fresh CSI-RS close to the CSIreporting time.

On the other hand, if Y is a large value, since it already takes a longtime from a triggering time to the report time, the time at which aCSI-RS measures a channel does not cause a critical problem compared tothe case where Y is small.

Therefore, in this case, the proposal 3 to be described later is notapplied but the time offset of the reference resource is configured byone of the following options.

First, the option 1 is described.

When a P/SP/AP CSI-RS is used to calculate CSI for A-CSI reporting, thetime offset of a CSI reference resource is derived from the Z value withrespect to a given CSI latency and numerology as described below.

In other words, n_(CQI_ref) is the same as ┌Z/N_(symb) ^(slot)┐ or isthe smallest value greater than or equal to ┌Z/N_(symb) ^(slot)┐, suchthat slot n−n_(CQI_ref) corresponds to a valid downlink slot.

The description above may be applied to P/SP CSI reporting in the sameway.

Next, the option 2 will be described.

When a P/SP/AP CSI-RS is used to calculate CSI for A-CSI reporting, thetime offset of a CSI reference resource is derived from the Z value withrespect to a given CSI latency and numerology as described below.

n_(CQI_ref) is the same as ┌Z/N_(symb) ^(slot)┐+1 or is the smallestvalue greater than or equal to ┌Z/N_(symb) ^(slot)┐+1, such that slotn−n_(CQI_ref) corresponds to a valid downlink slot.

The description above may be applied to P/SP CSI reporting in the sameway.

In the case of the option 2, the reference resource does not at allinclude symbols before 0, 1, 2, 3, . . . , Z symbols at the CSI reportstart time.

According to the current standard, since channel measurement orinterference measurement is not allowed to be performed after thereference resource, only the option 2 already satisfies the condition ofthe proposal 2.

Next, particulars related to aperiodic CSI report timing and CSIrelaxation will be described briefly.

Candidates of CSI calculation time Z are defined in Table 7 above.

While CSI is transmitted only on the PUSCH, if A-CSI reporting istriggered on slot n, the UE doesn't have to update the CSI with respectto A-CSI reporting for the following cases:

-   -   The case where M−L−N<Z for given CSI complexity and numerology        and    -   The case where an AP CSI-RS resource is transmitted on slot n        for given CSI complexity and numerology, and M−O−N<Z.

Here, L represents the last symbol of the PDCCH on slot n, M representsthe start symbol of the PUSCH, and N represents the TA value (forexample, TA=1.4 symbol) in units of symbols.

And O represents a later symbol between the last symbol of the AP CSI-RSresource for a channel measurement resource (CMR) and the last symbol ofthe AP CSI-RS resource for an interference measurement resource (IMR).

And the PUSCH timing offset for A-CSI reporting may be determined asfollows.

When the PUSCH is scheduled only for a single A-CSI report, the DCIfield for the PUSCH timing offset is defined from the Y in a reportsetting.

And when the PUSCH is scheduled only for a plurality of A-CSI reports,the DCI field for the PUSCH timing offset is defined as the maximumvalue among various Y values in the report setting.

For example, when Y={1, 2, 3, 6} in a report setting 1, and Y={2, 3, 4,5} in a report setting 2, Y may be defined as Y={2, 3, 4, 6}.

Other particulars defined in the standard will be described.

The terms of low complexity CSI and high complexity CSI may be replacedwith low latency CSI and high latency CSI, respectively.

Two CSI latency classes are supported for CSI computation capability.

The low latency CSI class is defined as WB CSI including a maximum offour antenna ports, which may be applied only when a Type-I codebook orPMI is not configured.

The high latency CSI class is defined as a superset of all of CSIsupported by the UE, and the descriptions given above are not applied toL1 RSRP.

And when CSI is transmitted through the PUSCH, a start and lengthindicator value (SLIV) and PUSCH mapping type are determined bypusch-symbolAllocation in the same way as in the PUSCH without CSI.

The PUSCH slot offset when CSI is multiplexed with the UL-SCH on thePUSCH is determined solely by the K2 value indicated bypusch-symbolAllocation rather than aperiodicReportSlotOffset.

The descriptions given above are applied only for the case where CSI ismultiplexed with data.

Here, the numbers of candidate values for the aperiodicReportSlotOffsetand K2 are the same with each other.

Particulars related to the A-CSI reporting will be further described.

The condition for when the UE does not need to update CSI for A-CSIreporting will be described again on the basis of the descriptions giveabove.

First, an A-CSI report trigger with respect to a plurality of CSI willbe described with the A-CSI report trigger with respect to single CSI inmind.

FIG. 12 illustrates one example of an A-CSI report trigger for singleCSI proposed by the present specification.

More specifically, FIG. 12 illustrates an example of an A-CSI reporttrigger with respect to single CSI, where a periodic CSI-RS and a CSIreference resource exist within a time window T.

In this case, the UE has to perform DCI decoding, channel estimation,CSI calculation, and Tx preparation within the time window T.

Therefore, when T<Z, the UE does not need to update the CSI.

FIG. 13 illustrates one example of an A-CSI report trigger for singleCSI having a periodic CSI-RS proposed by the present specification.

(Proposal 1)

In the case of an A-CSI report trigger for single CSI, the UE does notupdate the CSI when T<Z.

Here, T is a time duration between the reception time of the last OFDMsymbol of triggering DCI and the transmission time of the first OFDMsymbol of AP CSI reporting.

Different from FIG. 12, even though T>Z, FIG. 13 illustrates the case inwhich the P CSI-RS and the reference resource come late in the timewindow T.

In this case, even though T>Z, the UE is unable to complete CSIcalculation since it starts channel estimation too late.

Therefore, to prevent such a case from happening, the UE has to performchannel/interference measurement at the ZP/NZP CSI-RS at which at leastZ symbols are located before the first OFDM symbol of the AP CSI report.

(Proposal 2)

The UE does not need to measure channel or interference through theZP/NZP CSI-RS received from 0 to Z symbols before the transmission timeof the first OFDM symbol of the AP CSI report.

The time offset of the CSI reference resource has to be derived properlyfrom Z so that it matches the proposal 2.

FIGS. 14 and 15 illustrate examples of a method for determining a timeoffset of a CSI reference resource proposed by the presentspecification.

More specifically, FIGS. 14 and 15 illustrate two options fordetermining a time offset where Z=5, N_(symb) ^(slot)=14, and a CSIreport starts at the 10-th symbol of slot n.

FIG. 14 illustrates one example of valid CSI-RS locations for CSIreference resource and channel measurement when n_(CQI_ref)=┌Z/N_(symb)^(slot)┐.

In FIG. 14, since the reference resource is slot n−1, the UE is unableto use a potential CSI-RS resource at 1, 2, 3, or 4 symbol of slot n forchannel measurement.

The UE measures the channel from a CSI-RS at one or a few slots beforethe slot n.

However, this operation incurs too much delay between channelmeasurement and CSI report.

As a result, self-contained A-CSI feedback which is performed in thesame single slot in which CSI triggering, channel measurement, and CSIreport are conducted may not be supported.

To solve the aforementioned problem, as shown in FIG. 15, n_(CQI_ref)may be defined as └Z/N_(symb) ^(slot)┘.

In other words, FIG. 15 illustrates another example of valid CSI-RSlocations for CSI reference resource and channel measurement whenn_(CQI_ref)=└Z/N_(symb) ^(slot)┘.

In FIG. 15, the reference resource is slot n, and the slot n includes afew symbols beyond Z.

As a result, when the CSI-RS is transmitted on the 1st, 2nd, 3rd, or 4thsymbol of the slot n, the UE may measure the channel by using thetransmitted CSI-RS and calculate the CSI from the new channelmeasurement.

(Proposal 3)

When the P/SP/AP CSI-RS is used for CSI calculation for A-CSI reporting,the time offset of the CSI reference resource is derived from the Zvalue with respect to the CSI latency and numerology as given below.

Here, nCQI_ref is the smallest value greater than or equal to└Z/N_(symb) ^(slot)┘, such that slot n-nCQI_ref corresponds to a validdownlink slot.

Here, a specific slot may be regarded as a valid downlink slot when thefollowing conditions are satisfied:

-   -   When the specific slot includes a downlink or a flexible symbol        set on at least one upper layer,    -   When the specific slot is not located within a measurement gap        set for the UE,    -   When the active DL BWP in a slot is the same as the DL BWP for        which CSI report is conducted, and    -   When at least one CSI-RS transmission occasion for channel        measurement and CSI-RS for interference measurement and/or        CSI-IM occasion is located in the DRS active time no later than        the CSI reference resource in which the CSI report is conducted.

The description above may be applied to the P/SP CSI reporting in thesame way.

When an AP CSI-RS is transmitted, a problem similar to what has beendescribed with reference to FIG. 13 may occur, which will be describedwith reference to FIG. 16.

As shown in FIG. 13, it may be seen that the AP CSI-RS comes late in thetime window T.

In this case, even though T>Z, the UE is unable to complete CSIcalculation since it starts channel estimation too late.

A simple method to solve this problem is to compare T′ and Z instead ofT and Z.

Here, T′ represents a time gap between the most recent AP CSI-RSreception time and transmission time of the first OFDM symbol of the APCSI report.

In particular, if T′<Z, the UE updates CSI and does not have to reportthe lowest CQI.

In the case which requires more precise mechanism, Z′ which is smallerthan Z is defined, and instead of T′ and Z, T′ and Z′ may be compared.

In other words, Z′ indicates the amount of time required for channelmeasurement, CSI calculation, and TX preparation except for DCIdecoding.

Z indicates the time which includes DCI decoding in addition to thechannel measurement, CSI calculation, and TX preparation.

However, since the decoding time of DCI doesn't necessarily have to beconsidered in the T′, the time actually required for the T′ may besmaller than Z.

If sufficient time is not provided for T′, the UE does not havemeasurement of a channel under consideration, and thus the UE may reportthe lowest CQI in a specific UCI field.

FIG. 16 illustrates one example of an A-CSI report trigger for singleCSI having an aperiodic CSI-RS proposed by the present specification.

(Proposal 4)

In the case of A-CSI report trigger for single CSI which uses an APCSI-RS, if T′<Z, the UE does not need to calculate CSI and reports thelowest CQI.

Here, T′ represents a time duration between the most recent CSI-RSreception time and the transmission time of the first OFDM symbol for APCSI report.

In the case of A-CSI report trigger for a plurality of N CSI, if the UEis equipped with N parallel processors, the UE may use the samemechanism as in the single CSI trigger.

However, if more than N CSI is triggered, the UE is unable to completecalculation of all of the triggered CSI.

In this case, a CSI relaxation method supported by the LTE system may beused again.

(Proposal 5)

In other words, the proposal 5 reuses a relaxation method supported bythe LTE system in the case of an A-CSI report trigger for a plurality ofCSI.

Now, UE capability for CSI calculation will be described.

According to the proposals 1 to 3 described above, the amount of timerequired for CSI processing is determined, which may be summarized asshown in Tables 8 and 9.

In other words, Table 8 provides Z values for normal UEs, which arereference values that have to be supported by all of the UEs.

And Table 9 provides Z values for advanced UEs; therefore, for a givennumerology and CSI latency, UE capability is employed to report whetherto support the Z values of Table 9.

Also, for the given numerology and CSI latency, the Z values of Table 9have to be the same as or smaller than the Z values of Table 8.

Also, the value of Z′_(i,j) needs to be added with respect to Z′.

The Z′_(i,j) value represents a required time duration between thereception time of the most recent CSI-RS and the transmission time ofthe first OFDM symbol of the AP CSI report.

Table 8 illustrates one example of the CSI calculation time Z for normalUEs.

TABLE 8 CSI 15 kHz 30 kHz 60 kHz 120 kHz complexity Units SCS SCS SCSSCS Low latency Symbols Z_(1, 1) Z_(1, 2) Z_(1, 3) Z_(1, 4) CSI Highlatency Symbols Z_(2, 1) Z_(2, 2) Z_(2, 3) Z_(2, 4) CSI

Table 9 illustrates one example of CSI calculation time Z for advancedUEs.

TABLE 9 CSI 15 kHz 30 kHz 60 kHz 120 kHz complexity Units SCS SCS SCSSCS Low latency Symbols Z_(1, 1) Z_(1, 2) Z_(1, 3) Z_(1, 4) CSI Highlatency Symbols Z_(2, 1) Z_(2, 2) Z_(2, 3) Z_(2, 4) CSI

The proposals described above are summarized briefly as follows.

First, according to the proposal 1, if T<Z for an A-CSI report triggerwith respect to single CSI, the UE doesn't need to update CSI.

Here, T represents a time duration between the reception time of thelast OFDM symbol of triggering DCI and the transmission time of thefirst OFDM symbol of AP CSI reporting.

And according to the proposal 2, the UE doesn't need to measure achannel or interference due to a ZP/NZP CSI-RS received from 0 to Zsymbols before the transmission time of the first OFDM symbol of AP CSIreporting.

And according to the proposal 3, when a P/SP/AP CSI-RS is used toconduct CSI calculation for A-CSI reporting, the time offset of a CSIreference resource is derived from Z with respect to the given CSIlatency and numerology as follows.

In other words, n_(CQI_ref) is the smallest value greater than or equalto └Z/N_(symb) ^(slot)┘, such that slot n−n_(CQI_ref) corresponds to avalid downlink slot. This property may be applied in the same way toP/SP CSI reporting.

And according to the proposal 4, in the case of an A-CSI report triggerwith respect to single CSI which uses an AP CSI-RS, if T′<Z, the UEdoesn't need to calculate CSI and reports the lowest channel qualityindicator (CQI) to the eNB.

Here, T′ represents a time duration between the reception time of themost recent AP CSI-RS and the transmission time of the first OFDM symbolof the AP CSI report.

And the proposal 5 reuses a relaxation method supported by the LTEsystem in the case of an A-CSI report trigger for a plurality of CSI.

Next, another embodiment will be described.

The time offset of a CSI reference resource is derived from Z′ withrespect to the CSI latency and numerology given as follows.

n_(CQI_ref) is the smallest value greater than or equal to └Z′/N_(symb)^(slot)┘, such that slot n−n_(CQI_ref) corresponds to a valid downlinkslot.

Or n_(CQI_ref) may be interpreted to be the same as └Z′/N_(symb)^(slot)┘ or to be the smallest value among those values larger than└Z′/N_(symb) ^(slot)┘, such that slot n−n_(CQI_ref) corresponds to avalid downlink slot. This property may also be applied to at leastaperiodic CSI report.

And this property is applied when an AP/P/SP CSI-RS is used for CSIcalculation.

When a P/SP CSI-RS and/or CSI-IM is used for channel or interferencemeasurement, the UE does not expect the last OFDM symbol to measure achannel and/or interference with respect to the CSI-RS and/or CSI-IMreceived from 0 to Z′ symbols before the transmission time of the firstOFDM symbol of the AP CSI reporting.

The aforementioned property is not the only condition, and the CSI-RShas to be defined at or before the CSI reference resource. This propertyalso includes the case of the AP CSI-RS.

In the case of the AP CSI report, when the P/SP CSI-RS is used forchannel and/or interference measurement, the UE does not expect the mostrecent CSI-RS to be received later than the CSI reference resourcebefore triggering of the PDCCH.

In Table 10 below, (Z, Z′) values are reference values that have to besupported by all of the UEs.

For normal UEs, it has not been determined yet about whether the (Z, Z′)values with respect to low latency CSI and high latency CSI of Table 10below are the same with each other for given numerology.

If the two values are the same with each other for all of thenumerology, low latency and high latency are combined to normal UEs.

In Table 11 below, whether to support (Z, Z′) values of Table 11 withrespect to given numerology and CSI latency is reported to the eNBthrough UE capability.

For the given numerology and CSI latency, the (Z, Z′) values of Table 11have to be equal to or smaller than the (Z, Z′) values of Table 10.

Table 10 illustrates CSI calculation time Z for normal UEs.

TABLE 10 CSI 15 kHz 30 kHz 60 kHz 120 kHz complexity Units SCS SCS SCSSCS Low latency Symbols (Z_(1, 1), (Z_(1, 2), (Z_(1, 3), (Z_(1, 4),Z′_(1, 1)) Z′_(1, 2)) Z′_(1, 3)) Z′_(1, 4)) High latency Symbols(Z_(2, 1), (Z_(2, 2), (Z_(2, 3), (Z_(2, 4), Z′_(2, 1)) Z′_(2, 2))Z′_(2, 3)) Z′_(2, 4))

Table 11 illustrates CSI calculation time Z for advanced UEs.

TABLE 11 CSI 15 kHz 30 kHz 60 kHz 120 kHz complexity Units SCS SCS SCSSCS Low latency Symbols (Z_(1, 1), (Z_(1, 2), (Z_(1, 3), (Z_(1, 4),Z′_(1, 1)) Z′_(1, 2)) Z′_(1, 3)) Z′_(1, 4)) High latency Symbols(Z_(2, 1), (Z_(2, 2), (Z_(2, 3), (Z_(2, 4), Z′_(2, 1)) Z′_(2, 2))Z′_(2, 3)) Z′_(2, 4))

As yet another embodiment, a mechanism related to CSI reporting will bedescribed further.

More specifically, CSI reporting timing and UE capability relatedthereto will be described.

In what follows, through Tables 12 and 13, specific values of (Z, Z′)for a normal UE and an advanced UE will be examined.

For the Z′ value of a normal UE, it is assumed that the UE performs CSImeasurement/calculation and channel multiplexing; and CSI encoding andmodulation for the Z′ symbol.

Part of CSI measurement and calculation depends on the numerology andrequires 6*2(μ−2) symbols; the remaining portions and channelmultiplexing/CSI encoding/modulation uses 20 symbols respectively for ahigh latency and 13 symbols for a low latency.

As a result, Z′ for the low latency and the high latency is13+6*2{circumflex over ( )}(μ−2) and 20+6*2{circumflex over ( )}(μ−2).

For the Z value of a normal UE, it is assumed that a CSI-RS is locatedat the next symbol of a final PDCCH symbol.

Also, it is assumed that CSI processing may start after DCI decoding.

The DCI decoding time requires 4+10*2{circumflex over ( )}(μ−2)including a portion depending on a numerology such as PDCCHCE/demultiplexing/decoding and a portion independent of the numerology.

As a result, Z is determined by DCI decoding time+CSI processing time,namely 4+10*2 (μ−2)+Z′.

In the case of an advanced UE, since DCI decoding is conducted for 5symbols, Z′ is 7 symbols and 14 symbols, respectively for a low latencyand a high latency; and Z is Z′+5.

Table 12 represents CSI calculation time (Z, Z′) for a normal UE.

TABLE 12 15 kHz 30 kHz 60 kHz 120 kHz CSI SCS SCS SCS SCS complexityUnits (μ = 0) (μ = 1) (μ = 2) (μ = 3) Low latency Symbols (22, 15) (25,16) (33, 19) (49, 25) High latency Symbols (29, 22) (32, 23) (40, 26)(56, 32)

Table 13 represents CSI calculation time (Z, Z′) for an advanced UE.

TABLE 13 15 kHz 30 kHz 60 kHz 120 kHz CSI SCS SCS SCS SCS complexityUnits (μ = 0) (μ = 1) (μ = 2) (μ = 3) Low latency Symbols (12, 7) (12,7) (12, 7) (12, 7) High latency Symbols (19, 14) (19, 14) (19, 14) (19,14)

Various proposals related to the descriptions above will be examined.

The proposals to be described later may be applied separately from theproposals described above or applied together with the aforementionedproposals.

(Proposal 1′)

As the minimum required CSI processing time for a normal and an advancedUEs, the (Z, Z′) values of Tables 12 and 13 above are selected,respectively.

Regarding CSI and data multiplexing, one remaining problem is the numberof symbols required for a UE to complete CSI processing and dataencoding simultaneously.

When CSI and data are multiplexed, allocation of a data resource element(RE) depends on a CSI payload; however, CSI/payload size is variedaccording to CRI/RI/amplitude coefficient other than 0, or the number ofCSI omission.

As a result, CSI processing and data encoding may not be performed in afully parallel manner.

More specifically, in the case of type I CSI, CRI/RI of Part 1determines the payload size of Part 2 CSI such as PMI and CQI.

In the case of type II CSI, the number of non-zero amplitudecoefficients of RI/Part 1 CSI determines the payload size of Part 2 CSIsuch as PMI and CQI.

Therefore, when CSI and data are multiplexed, instead of (Z, Z′), the UErequires at least (Z+C, Z′+C) symbol to prepare CSI and datasimultaneously.

Here, C is smaller than or equal to N2.

(Proposal 2′)

When AP CSI and data for a PUSCH are multiplexed, the UE is not expectedto receive scheduling DCI having a symbol offset such that M−L−N<Z+C.

Here, L represents the last symbol of a PDCCH triggering an A-CSIreport, L is a start symbol of a PUSCH, N is a TA value in symbol units,and C is equal to or smaller than N2.

(Proposal 3′)

When AP CSI and data for a PUSCH are multiplexed, and an AP CSI-RS isused for channel measurement, the UE is not expected to receivescheduling DCI having a symbol offset such that M−O−N<Z′+C.

Here, N represents a TA value in symbol units; O represents a valuewhich comes late among the last symbol of an AP CSI-RS resource for aCMR, the last symbol of an aperiodic NZP CSI-RS for an IM (if exists),and the last symbol of an aperiodic CSI-IM (if exists); and C is equalto or smaller than N2.

Also, when AP CSI and data for a PUSCH are multiplexed, although thetime position of a CSI reference resource is determined in the samemanner for the AP CSI only case, the time position is determined basedon Z′+C instead of Z′.

(Proposal 4′)

When AP CSI and data for a PUSCH are multiplexed, a time offset of a CSIreference resource is derived from Z′+C with respect to a given CSIlatency and a numerology.

The time offset of a CSI reference resource is derived from Z′ withrespect to a given CSI latency and a numerology as follows.

n_(CQI_ref) is the smallest value greater than or equal to└(Z′+C)/N_(symb) ^(slot)┘, such that slot n−n_(CQI_ref) corresponds to avalid downlink slot.

When a P/SP CSI-RS and/or CSI-IM is used for channel measurement and/orinterference measurement, the UE does not expect the last OFDM symbol tomeasure a channel and/or interference with respect to the CSI-RS and/orCSI-IM received from 0 to Z′+C symbols before the transmission time ofthe first OFDM symbol of an AP CSI report.

Another issue is calculation time for a beam report, namely CRI andlayer 1 reference signal received power (L1 RSRP).

When L1 RSRP is power measurement of a single port, and the samecalculated power is used for a CSI report and a beam report, it ispreferable to regard the L1 RSRP as low latency CSI.

Also, to reduce calculation complexity, the number of CSI-RS resourcesfor a beam report may be limited.

(Proposal 5′)

The same (Z, Z′) is applied for a beam report from low latency CSI as inthe CSI report.

Next, in the case of an A-CSI report trigger for a plurality of N CSI,if the UE is equipped with X parallel processors, and X≥N, the samemechanism as a single CSI report trigger may be used without relaxation.

However, if more than X CSIs are triggered, the UE is unable to completethe calculation for all of the triggered CSIs.

In this case, a relaxation method supported in the LTE system may bereused.

In particular, if the UE does not have an unreported CSI(s), and N>X,the UE does not necessarily have to calculate N−X CSI(s).

(Proposal 6′)

In the case of an A-CSI report trigger for a plurality of CSI, arelaxation method supported in the LTE system may be reused.

More specifically, if the UE is equipped with X parallel CSI processorsand have N unreported CSI(s), and N>X, the UE does not necessarily haveto update N−X most recent CSI(s).

Regarding the time position of a reference resource for P/SP CSIreporting, the same method for the time position of a reference resourcefor AP CSI reporting may be applied.

(Proposal 7′)

The reference resource time position for P/SP CSI reporting may bedetermined by the same method for the reference resource time positionfor AP CSI reporting.

Particulars related to CSI relaxation will be described in more detail.

X represents capability for the maximum number of CSIs that may beupdated simultaneously.

If CSI processing time intervals of N (>X) CSI reports overlap with eachother in the time domain, the UE does not need to update N−X CSIreports.

A CSI processing time interval is a time interval which ranges from thestart of a symbol S to the last of a symbol E.

Here, regarding periodic and semi-persistent CSI reporting,

(1) In the case of Alt. 1,

S is a start symbol of a CQI reference resource slot.

(2) In the case of Alt. 2,

S is E−Z′ (or E−(Z′+1)), and E is a start symbol of a CSI report.

Since the NR sets the location of a channel measurable CSI-RS at thesymbol level (in other words, a CSI-RS located at a symbol below E−Z′ orat a symbol below E−(Z′+1) is measured), Alt. 2 proposes the latest timeat which CSI processing may be started.

In other words, the UE may start CSI processing at the time S of Alt. 2at the latest.

(3) In the case of Alt. 3,

S is the location of the start symbol of a CSI report—Z′ (or startsymbol of a CSI report—(Z′+1)) or the last symbol of the CSI-RS (whichis used for calculation of the corresponding CSI) received at the mostrecent time point among the time points before the start symbol.

Since the UE starts CSI calculation by using the CSI-RS at theaforementioned time point, the UE is appropriate for S and satisfiesthat E=S+Z′.

Next, regarding a CSI report and a CSI-IM having a periodic orsemi-persistent CSI-RS,

(1) In the case of Alt. 1,

If a reference resource is located before a PUCCH with aperiodic CSItriggering, S becomes the last symbol of the PDCCH with aperiodic CSItriggering, and E=S+Z.

Otherwise, S=E−Z′, and E is the start symbol of a CSI report.

(2) In the case of Alt. 2,

If the start symbol of a CSI report—Z′ (or start symbol of a CSIreport—(Z′+1)) is located before the PDCCH with aperiodic CSItriggering, S is the last symbol with aperiodic CSI triggering (or S isthe last symbol of the PDCCH with aperiodic CSI triggering+1), andE=S+Z.

In other words, if a measurable CSI-RS is received before the PDCCH, theUE may start CSI calculation after receiving the PDCCH.

Since the minimum required time until a CSI report is completed afterreception of the PDCCH is Z, the time at which the CSI calculation isfinished becomes S+Z.

Otherwise, S is E−Z′ (or E−(Z′+1)), and E is the start symbol of a CSIreport.

In other words, if a measurable CSI-RS is received after the PDCCH, theUE may start CSI calculation after receiving the CSI-RS.

Since the minimum required time until the CSI report is completed afterreception of the CSI-RS is Z′, the time at which CSI calculation isfinished becomes S+Z′.

(3) In the case of Alt. 3,

Suppose the most recent CSI-RS received at or before the start symbol ofCSI report—Z′ (or start symbol of CSI report—(Z′+1)) is a ‘referenceCSI-RS’. If the last symbol of a reference CSI-RS is located before thePDCCH with aperiodic CSI triggering, S becomes the last symbol of thePDCCH with aperiodic CSI triggering (or last symbol of the PDCCH withaperiodic CSI triggering+1), and E=S+Z.

In other words, if a measurable CSI-RS is received before the PDCCH, theUE may start CSI calculation after receiving the PDCCH.

Since the minimum required time until a CSI report is completed afterreception of the PDCCH is Z, the time at which CSI calculation isfinished becomes S+Z.

Otherwise, S=E−Z′ (or E−(Z′+1)), and E is the start symbol of a CSIreport.

In other words, if a measurable CSI-RS is received after the PDCCH, theUE may start CSI calculation after receiving the CSI-RS.

Since the minimum required time until a CSI report is completed afterreceiving the CSI-RS is Z′, the time at which CSI calculation isfinished becomes S+Z′.

(4) In the case of Alt. 4,

S is E−Z′ (or E−(Z′+1)), and E is the start symbol of a CSI report.

Next, regarding an aperiodic CSI report with an aperiodic CSI-RS and aCSI-IM,

S1 is the last symbol of a PDCCH with aperiodic CSI triggering.

S2 is the symbol which comes late among the last symbol of an aperiodicCSI-RS with respect to a CMR, the last symbol of the aperiodic CSI-RSwith respect to an IMR, and the last symbol of the aperiodic CSI-IM.

(1) In the case of Alt. 1,

If S1+Z>S2+Z′ (in other words, if the location of an OFDM symbol addedby Z symbols in S1 lies after the OFDM symbol location added by Z′symbols in S2), S=S1, and E=S1+Z.

Otherwise, S=S2, and E=S2+Z′.

The UE terminates CSI processing at a later time between S1+Z and S2+Z′.

Therefore, E is set to the later of the two, and the start time of whichis completed later between the two is assumed to be the start of CSIprocessing.

(2) In the case of Alt. 2,

It is set such that S=S2.

If S1+Z>S2+Z (in other words, if the location of an OFDM symbol added byZ symbols in S1 lies after the OFDM symbol location added by Z′ symbolsin S2), E=S1+Z. Otherwise, E=S2+Z′.

Here, the end time of CSI processing in Alt. 2 is the same as that ofAlt. 1, but the start time is fixed to S2 which is used for channeland/or interference estimation.

This is so because an AP CSI-RS is always restricted to be receivedafter reception of a PDCCH, and in this case, the UE is able to startCSI processing at least when the reception of the CSI-RS is completed.

(3) In the case of Alt. 3,

S is E−Z′ (or E−(Z′+1)), and E is the start symbol of a CSI report.

When CSI is calculated by using a P/SP CSI-RS and/or CSI-InterferenceMeasurement (IM), a plurality of measurable CSI-RSs may exist in thetime domain.

The UE may calculate CSI by measuring a CSI-RS received as recently aspossible with respect to a CSI reporting time, thereby obtaining freshCSI.

At this time, too, a CSI-RS located before reporting time—Z′ has to bemeasured by taking into account the CSI calculation time of the UE.

However, if the CSI (which is called ‘CSI 1’) calculation time overlapswith other CSI (which is called ‘CSI 2’) calculation time, and thenumber of CSIs that may be calculated at the same time is exceeded, theUE is unable to calculate part of CSIs.

To solve the problem above, the calculation time of CSI 1 may be put toan earlier time so that it may not be overlapped with the CSI 2.

This is possible since the CSI 1 is calculated by using a P/SP CSI-RSand/or CSI-IM, a plurality of P/SP CSI-RSs and/or CSI-IMs exist alongthe time axis, and thereby the CSI 1 may be calculated in advance byusing the P/SP CSI-RS and/or CSI-IM received previously.

However, it should be noted that if the CSI 1 is calculated too early, apotential interval is introduced to avoid a situation where CSI isoutdated, and the CSI 1 may be calculated in advance by using the P/SPCSI-RS and/or CSI-IM received within the potential interval.

A potential interval (namely the N value proposed below) may bedetermined by the eNB and indicated for the UE; or the UE may determinethe potential interval and report the determined potential interval tothe eNB.

The potential interval is terminated at “reporting time—Z′” and startsat the end time—N time.

When a plurality of CSIs are reported through the same PUSCH, channelmultiplexing/encoding/modulation is performed simultaneously to aplurality of the corresponding CSIs, and therefore, a smaller amount ofprocessing time is required than the case where a plurality of CSIs arereported through a different PUSCH.

Therefore, when a plurality of CSIs are reported through the same PUSCH,one of the CSIs requires CSI processing time T, but the remaining CSI(s)requires only the time needed for “T—channelmultiplexing/encoding/modulation”.

Therefore, when processing time is defined for CSI relaxation, theremaining CSI is defined as “T-channelmultiplexing/encoding/modulation”, and as a result, the possibility thatthe processing time overlaps with other CSI may be reduced.

And when channel and/or interference is measured by using a periodic orsemi-persistent CSI-RS, a plurality of measurable CSI-RSs may existalong the time axis.

In this case, the UE calculates CSI by measuring a CSI-RS existingbefore Z′ (or Z′+1) symbol with reference to the first OFDM symbol whichstarts CSI reporting.

Therefore, the latest time at which the UE measures CSI for CSIcalculation becomes “the symbol before Z′ (or Z′+1) symbols withreference to the first OFDM symbol which starts CSI reporting”.

Therefore, it is preferable to set the start time of CSI processing as“the symbol before Z′ (or Z′+1) symbols with reference to the first OFDMsymbol which starts CSI reporting”.

And it is preferable to set the end time of CSI processing as the firstOFDM symbol which starts CSI reporting.

On the other hand, when channel and/or interference is measured by usingan aperiodic CSI-RS, one measurable CSI-RS may exist along the timeaxis.

Therefore, it is preferable to set the start time of CSI processing as“the very last symbol at which an AP CSI-RS and/or AP CSI-IM isreceived”.

In the case of periodic or semi-persistent CSI reporting, a reportingtime is defined in advance.

Therefore, the UE knows the location of a recent CSI-RS existing beforeZ′ (or Z′+1) symbol with reference to the first OFDM symbol which startsCSI reporting.

Therefore, since calculation may be started from the correspondingCSI-RS, S becomes the last OFDM symbol of the corresponding CSI-RS, andE becomes S+Z′.

In the case of AP CSI reporting, when an AP CSI-RS is used, one CSI-RSused for CSI calculation exists along the time axis.

It should be noted that since a CSI-RS for CMR uses is different from aCSI-RS for IMR uses, there exist one CSI-RS for each use along the timeaxis.

Therefore, since calculation may be started from the correspondingCSI-RS, S becomes the last OFDM symbol of the corresponding CSI-RS, andE becomes S+Z′.

In the case of AP CSI reporting, when a P/SP CSI-RS is used, the mostrecent CSI-RS used for CSI calculation may be received before DCI.

Therefore, if the last OFDM symbol of the corresponding CSI-RS is set toS, the UE starts to calculate CSI at a time at which it is uncertainwhether the corresponding CSI may be triggered or not.

If the corresponding CSI is not triggered, the UE wastes computationpower, and a problem may arise, such that the corresponding computationpower is not used for other CSI calculation.

To solve the problem above, S is defined such that S=E−Z′, and E isdefined as the first symbol of PUSCH CSI reporting.

Various combinations are possible for S and E proposed in the differentAlt.s, above, and corresponding combinations are also applicable to amethod proposed by the present specification.

For example, S and E may be determined by the S of Alt. 1 and the E ofAlt. 2.

And in the proposals 2 and 3 above, Z′ may be replaced with Z′−1.

Since the UE may still be able to calculate CSI even if Z′ time isgiven, which ranges from a CSI-RS and/or CSI-IM to the start symbol ofCSI reporting, Z′ may be replaced with Z′−1.

For the same reason, in the proposal 4 above, Z′ may be replaced withZ′−1.

Method for Operating a UE and an eNB

In what follows, operations of a UE and an eNB for performing the methodabove proposed in the present specification will be described withreference to FIGS. 17 to 23.

FIG. 17 is a flow diagram illustrating one example of a method foroperating a UE which performs CSI reporting proposed by the presentspecification.

First, the UE receives downlink control information (DCI) triggering anaperiodic CSI report from the eNB S1710.

And the UE determines a CSI reference resource related to the aperiodicCSI report S1720.

The CSI reference resource may be determined to a slot n−n_(CQI_ref) inthe time domain.

More specifically, the n_(CQI_ref) may be the smallest value equal to orgreater than floor(a first parameter/a second parameter) so that theslot n−n_(CQI_ref) corresponds to a valid downlink slot.

Here, a specific slot may be regarded as a valid downlink slot when thefollowing conditions are satisfied:

-   -   The case where the specific slot includes a downlink or flexible        symbol set to at least one upper layer,    -   The case where the specific slot is not located within a        measurement gap configured for the UE,    -   The case where an active DL BWP in the slot is the same as a DL        BWP in which a CSI report is conducted, and    -   The case where there exists at least one CSI-RS transmission        occasion and CSI-RS and/or CSI-IM occasion for interference        measurement at a DRS active time no later than a CSI reference        resource at which a CSI report is conducted.

Here, the first parameter may be related to the time for computation ofthe CSI, and the second parameter may represent the number of symbolswithin one slot.

More specifically, the first parameter may be represented by a specificnumber of symbols (Z′), and the second parameter may be represented byN_(symb) ^(slot).

And the second parameter is 14.

And the first parameter may be determined based on a CSI latency and anumerology.

The CSI latency may be represented by a CSI computation delay.

And the UE reports the CSI to the eNB on slot n based on the CSIreference resource S1730.

In addition, the UE receives, from the eNB, an aperiodic CSI-RS.

And the UE computes the CSI based on the aperiodic CSI-RS and the CSIreference resource.

It is preferable to conduct the process for computing the CSI before theS1730 step.

Here, the aperiodic CSI-RS may be received after the DCI.

Also, the UE may transmit capability information including the firstparameter to the eNB before the S1710 step.

The DCI may be received in a slot other than the slot n.

The operation of the UE of FIG. 17 may be interpreted as follows.

The UE receives, from a base station (BS), downlink control information(DCI) related to an aperiodic CSI report that is to be performed by theUE in a slot n.

And, the UE determines a value n_(CQI_ref) based on a number of symbolsZ′ related to a time for computing the CSI.

And, the UE determines a CSI reference resource as being a slotn−n_(CQI_ref) in a time domain that is to be used for the aperiodic CSIreport.

And, the UE transmits, to the BS, the aperiodic CSI report in the slotn, based on the CSI reference resource being slot n−n_(CQI_ref).

The n_(CQI_ref) is a smallest value greater than or equal to└Z′/N_(symb) ^(slot)┘ such that the slot n−n_(CQI_ref) satisfies a validdownlink slot criteria.

Here, └·┘ is a floor function and N_(symb) ^(slot) is a number ofsymbols in one slot.

The valid downlink slot criteria is based at least on (i) the number ofsymbols Z′ related to the time for computing the CSI and (ii) a DCIprocessing time.

The N_(symb) ^(slot) is equal to 14 symbols in a slot.

Additionally, the UE may receive, from the BS, an aperiodic referencesignal (CSI-RS) in the CSI reference resource, slot n−n_(CQI_ref), anddetermine the CSI based on the aperiodic CSI-RS, and generate theaperiodic CSI report based on the CSI.

And, the UE may determine the number of symbols Z′ related to the timefor computing the CSI based on a CSI complexity and a subcarrierspacing.

The number of symbols Z′ does not include a DCI processing time.

And, the UE determines the value n_(CQI_ref) based on the number ofsymbols Z′ related to the time for computing the CSI, and further basedon a number of symbols in one slot.

Also, the UE may receive the DCI in a slot other than the slot n inwhich the aperiodic CSI report is to be performed.

Also, based on the value n_(CQI_ref) being equal to zero, the aperiodicCSI report may be performed in a same slot as receiving the DCI.

FIG. 18 is a flow diagram illustrating one example of a method foroperating an eNB which receives a CSI report proposed by the presentspecification.

First, the eNB transmits downlink control information (DCI) triggeringan aperiodic CSI report to the UE S1810.

And the eNB receives, from the UE, the aperiodic CSI report on slot nS1820.

Here, the aperiodic CSI report is related to a CSI reference resource,and the CSI reference resource may be determined to a slot n−n_(CQI_ref)in the time domain.

At this time, the n_(CQI_ref) may be the smallest value equal to orgreater than floor (a first parameter/a second parameter) so that theslot n−n_(CQI_ref) corresponds to a valid downlink slot.

Here, the first parameter may be related to the time for computation ofthe CSI, and the second parameter may represent the number of symbolswithin one slot.

More specifically, the first parameter may be represented by a specificnumber of symbols (Z′), and the second parameter may be represented byN_(symb) ^(slot).

And the second parameter is 14.

And the first parameter may be determined based on a CSI latency and anumerology.

The CSI latency may be represented by a CSI computation delay.

In addition, the eNB may transmit an aperiodic CSI-RS to the UE.

At this time, the aperiodic CSI-RS may be transmitted to the UE afterthe DCI.

And the eNB may receive, from the UE, capability information includingthe first parameter before the S1810 step.

Here, the DCI may be transmitted from a slot other than the slot n.

Referring to FIGS. 19 to 23 to be described later, a process by which amethod for reporting CSI proposed in the present specification isimplemented in a UE will be described in more detail.

First, in a wireless communication system, a UE for reporting CSI maycomprise an Radio Frequency (RF) module for transmitting and receiving aradio signal; and a processor operatively connected to the RF module.

The RF module of the UE receives, from the eNB, downlink controlinformation (DCI) triggering an aperiodic CSI report.

And the processor controls the UE to determine a CSI reference resourcerelated to the aperiodic CSI report.

The CSI reference resource may be determined to a slot n−n_(CQI_ref) inthe time domain.

The n_(CQI_ref) may be determined based on a first parameter related tothe time for computing the CSI.

And the first parameter may be determined based on a CSI latency and anumerology.

The CSI latency may be represented by a CSI computation delay.

More specifically, the n_(CQI_ref) may be the smallest value equal to orgreater than floor(a first parameter/a second parameter) so that theslot n−n_(CQI_ref) corresponds to a valid downlink slot.

The second parameter may represent the number of symbols within oneslot.

More specifically, the first parameter may be represented by a specificnumber of symbols (Z′), and the second parameter may be represented byN_(symb) ^(slot).

And the second parameter is 14.

Now, a specific method for computing a n_(CQI_ref) value by the UE willbe described with reference to FIG. 19.

In other words, FIG. 19 illustrates one example of a method forimplementing a n_(CQI_ref) value proposed in the present specification.

First, the memory of a UE stores a predefined second parameter.

And the processor of the UE may compute the n_(CQI_ref) value by usingan input first parameter value and a second parameter value stored inthe memory.

The first parameter value is determined based on a CSI latency (or CSIcomputation delay) and a numerology (μ).

As shown in FIG. 19, in the case of CSI latency 1, if the numerology (μ)is 0, 1, 2, and 3, the first parameter value is 8, 11, 21, and 36,respectively, and the n_(CQI_ref) value corresponding thereto is 0, 0,1, and 2.

And in the case of CSI latency 2-1, if the numerology (μ) is 0, 1, 2,and 3, the first parameter value is 16, 30, 42, and 85, respectively,and the n_(CQI_ref) value corresponding thereto is 1, 2, 3, and 6.

And in the case of CSI latency 2-2, if the numerology (μ) is 0, 1, 2,and 3, the first parameter value is 37, 69, 140, and 140, respectively,and the n_(CQI_ref) value corresponding thereto is 2, 4, 10, and 10.

And the RF module of the UE reports the CSI to the eNB on slot n basedon the CSI reference resource.

In addition, the RF module of the UE receives, from the eNB, anaperiodic CSI-RS.

And the processor of the UE computes the CSI based on the aperiodicCSI-RS and the CSI reference resource.

It is preferable that the processor of the UE performs computation ofCSI before the RF module of the UE reports the CSI.

Here, the aperiodic CSI-RS may be received after the DCI.

Also, the RF module of the UE may transmit capability informationincluding the first parameter to the eNB before receiving the DCI.

The DCI may be received in a slot other than the slot n.

Referring to FIGS. 19 to 23 to be described later, a process by which amethod for reporting CSI proposed in the present specification isimplemented in an eNB will be described in more detail.

First, in a wireless communication system, an eNB for receiving a CSIreport may comprise a Radio Frequency (RF) module for transmitting andreceiving a radio signal; and a processor operatively connected to theRF module.

First, the RF module of the eNB transmits to the UE downlink controlinformation (DCI) triggering an aperiodic CSI report.

And the RF module of the eNB receives, from the UE, the aperiodic CSIreport on a slot n.

Here, the aperiodic CSI report is related to a CSI reference resource,and the CSI reference resource may be determined to a slot n−n_(CQI_ref)in the time domain.

At this time, the n_(CQI_ref) may be the smallest value equal to orgreater than floor(a first parameter/a second parameter) so that theslot n−n_(CQI_ref) corresponds to a valid downlink slot.

Here, the first parameter may be related to time for computing the CSI,and the second parameter may represent the number of symbols in oneslot.

More specifically, the first parameter may be represented by a specificnumber of symbols (Z′), and the second parameter may be represented byN_(symb) ^(slot).

And the second parameter may be 14.

And the first parameter may be determined based on a CSI latency and anumerology.

The CSI latency may be represented by a CSI computation delay.

In addition, the RF module of the UE may transmit an aperiodic CSI-RS tothe UE.

At this time, the aperiodic CSI-RS may be transmitted to the UE afterthe DCI.

And the RF module of the eNB may receive capability informationincluding the first parameter from the UE before transmitting the DCI.

Here, the DCI may be transmitted from a slot other than the slot n.

The Device to which the Present Invention May be Applied in General

FIG. 20 illustrates a block diagram of a wireless communication deviceto which methods proposed by the present specification may be applied.

Referring to FIG. 20, a wireless communication system comprises an eNB2010 and a plurality of UEs 2020 located within the range of the eNB3510.

The eNB and the UEs may be represented by wireless devices,respectively.

The eNB comprises a processor 2011, memory 2012, and Radio Frequency(RF) unit 2013. The processor 2011 implements the functions, processesand/or methods described with reference to FIGS. 1 to 19. Layers of awireless interface protocol may be implemented by the processor. Thememory, being connected to the processor, stores various kinds ofinformation to operate the processor. The RF unit, being connected tothe processor, transmits and/or receives a radio signal.

The UE comprises a processor 2021, memory 2022, and RF unit 2023.

The processor implements the functions, processes and/or methodsdescribed with reference to FIGS. 1 to 19. Layers of a wirelessinterface protocol may be implemented by the processor. The memory,being connected to the processor, stores various kinds of information tooperate the processor. The RF unit, being connected to the processor,transmits and/or receives a radio signal.

The memory 2012, 2022 may be installed inside or outside the processor2011, 2021 and may be connected to the processor via various well-knownmeans.

Also, the eNB and/or the UE may be equipped with a single antenna ormultiple antennas.

The antenna 2014, 2024 performs the function of transmitting andreceiving a radio signal.

FIG. 21 illustrates a block diagram of a communication device accordingto one embodiment of the present invention.

In particular, FIG. 21 provides further details of the UE of FIG. 20.

Referring to FIG. 21, the UE may comprise a processor (or digital signalprocessor (DSP)) 2110, RF module (or RF unit) 2135, power managementmodule 2105, antenna 2140, battery 2155, display 2115, keypad 2120,memory 2130, Subscriber Identification Module (SIM) card 2125 (thiselement is optional), speaker 2145, and microphone 2150. The UE may alsoinclude a single antenna or multiple antennas.

The processor 2110 implements the functions, processes and/or methodsdescribed with reference to FIGS. 1 to 19. Layers of a wirelessinterface protocol may be implemented by the processor.

The memory 2130 is connected to the processor and stores informationrelated to the operation of the processor. The memory may be installedinside or outside the processor and may be connected to the processorvia various well-known means.

The user, for example, enters command information such as a phone numberby pushing (or touching) the button of the keypad 2120 or via voiceactivation by using the microphone 2150. The processor receives thecommand information and processes the command to perform an appropriatefunction such as making a phone call to the phone number. Operationaldata may be extracted from the SIM card 2125 or memory 2130. Also, theprocessor may recognize the user and for the convenience of the user,may display command information or operational information on thedisplay 2115.

The RF unit 2135, being connected to the processor, transmits and/orreceives an RF signal. The processor delivers command information to theRF module to initiate communication, for example, to transmit a radiosignal comprising voice communication data. The RF module is composed ofa receiver and a transmitter for receiving and transmitting a radiosignal. The antenna 2140 performs the function of transmitting andreceiving a radio signal. When receiving a radio signal, the RF moduledelivers a signal and transforms the signal into the baseband so thatthe processor may process the signal. The processed signal may beconverted to audible information output through the speaker 2145 orreadable information.

FIG. 22 illustrates one example of an RF module of a wirelesscommunication device to which a method proposed by the presentspecification may be applied.

More specifically, FIG. 22 illustrates one example of an RF module whichmay be implemented in a Frequency Division Duplex (FDD) system.

First, along the transmission path, the processor shown in FIGS. 20 and21 processes data to be transmitted and provides an analog output signalto the transmitter 2210.

Within the transmitter 2210, the analog output signal is filtered by thelow pass filter (LPF) 2211 to remove images caused by theanalog-to-digital converter (ADC), up-converted to an RF band from thebaseband by the mixer 2212, and amplified by the variable gain amplifier(VGA) 2213; the amplified signal is filtered by the filter 2214,additionally amplified by the power amplifier (PA) 2215, routed througha duplexer(s) 2250/antenna switch(es) 2260, and transmitted through theantenna 2270.

Also, along the reception path, the antenna receives signals from theoutside and provides the received signals, which are routed through theantenna switch(es) 2260/duplexers 2250 and are provided to the receiver2220.

Within the receiver 2220, received signal are amplified by the low noiseamplifier (LNA) 2223, filtered by the bandpass filter 2224, anddown-converted to the baseband from the RF band by the mixer 2225.

The down-converted signal is filtered by the low pass filter (LPF) 2226,amplified by the VGA 2227 to acquire the analog input signal, which isprovided to the processor illustrated in FIGS. 20 and 21.

Also, the local oscillator (LO) 2240 generates transmission andreception LO signals and provides the generated signals to the upconverter 2212 and down converter 2225, respectively.

Also, the phase locked loop (PLL) 2230 receives control information fromthe processor to generate transmission and reception LO signals atappropriate frequencies and provides the control signals to the LOgenerator 2240.

Also, the circuits shown in FIG. 22 may be arranged differently from thestructure of FIG. 22.

FIG. 23 illustrates another example of an RF module of a wirelesscommunication device to which a method proposed by the presentspecification may be applied.

More specifically, FIG. 23 illustrates one example of an RF module whichmay be implemented in a Time Division Duplex (TDD) system.

The transmitter 2310 and the receiver 2320 of the RF module in the TDDsystem have the same structures as those of a transmitter and a receiverof an RF module in the FDD system.

In what follows, only the structure of the RF module in the TDD systemwhich exhibits a difference from the RF module in the FDD system will beillustrated, and the same structure thereof will be described withreference to FIG. 22.

A signal amplified by the power amplifier 2315 of the transmitter isrouted via the band select switch 2350, bandpass filter (BPF) 2360, andantenna switch(es) 2370; and is transmitted through the antenna 2380.

Also, along the reception path, the antenna receives signals from theoutside, provides the received signals. The signals are routed via theantenna switch(es) 2370, BPF 2360, and band select switch 2350; and areprovided to the receiver 2320.

The embodiments described above are combinations of constitutingelements and features of the present invention in a predetermined form.Each individual element or feature has to be considered as optionalexcept where otherwise explicitly indicated. Each individual element orfeature may be implemented solely without being combined with otherelements or features. Also, it is also possible to construct theembodiments of the present invention by combining a portion of theelements and/or features. A portion of a structure or feature of anembodiment may be included in another embodiment or may be replaced withthe corresponding structure of feature of another embodiment. It shouldbe clearly understood that the claims which are not explicitly citedwithin the technical scope of the present invention may be combined toform an embodiment or may be included in a new claim by an amendmentafter application.

The embodiments of the present invention may be implemented by variousmeans such as hardware, firmware, software, or a combination thereof. Inthe case of hardware implementation, one embodiment of the presentinvention may be implemented by using one or more of ASICs (ApplicationSpecific Integrated Circuits), DPSs (Digital Signal Processors), DSPDs(Digital Signal Processing Devices), PLDs (Programmable Logic Devices),FPGAs (Field Programmable Gate Arrays), processors, controllers,micro-controllers, and micro-processors.

In the case of implementation by firmware or software, one embodiment ofthe present invention may be implemented in the form of modules,procedures, functions, and the like which perform the functions oroperations described above. Software codes may be stored in the memoryand activated by the processor. The memory may be located inside oroutside of the processor and may exchange data with the processor byusing various well-known means.

It is apparent for those skilled in the art that the present inventionmay be embodied in other specific forms without departing from theessential characteristics of the present invention. Therefore, thedetailed descriptions above should be regarded as being illustrativerather than restrictive in every aspect. The technical scope of thepresent invention should be determined by a reasonable interpretation ofthe appended claims, and all of the modifications that fall within anequivalent scope of the present invention belong to the technical scopeof the present invention.

This document discloses a method for reporting CSI in a wirelesscommunication system with examples based on the 3GPP LTE/LTE-A systemand the 5G system (New RAT system); however, the present invention maybe applied to various other types of wireless communication systems inaddition to the 3GPP LTE/LTE-A system and the 5G system.

The present invention determines a CSI reference resource as close aspossible to a CSI reporting time, thereby preventing a resource (a fewsymbols) from being wasted without being used and reporting the mostrecent CSI by computing CSI based on the most recently received CSI-RS.

The technical effects of the present invention are not limited to thetechnical effects described above, and other technical effects notmentioned herein may be understood to those skilled in the art to whichthe present invention belongs from the description below.

What is claimed is:
 1. A method of receiving, by a base station (BS), achannel state information (CSI) report in a wireless communicationsystem, the method comprising: transmitting, by the BS and to a userequipment (UE), downlink control information (DCI) related to anaperiodic CSI report that is to be received by the UE in a slot n; andreceiving, by the BS and from the UE, the aperiodic CSI report in theslot n, based on a CSI reference resource being slot n−n_(CQI_ref) in atime domain, wherein the CSI reference resource in the slotn−n_(CQI_ref) is to be used for the aperiodic CSI report, whereinn_(CQI_ref) is a smallest value greater than or equal to └Z′/N_(symb)^(slot)┘ such that the slot n−n_(CQI_ref) satisfies a valid downlinkslot criteria, and wherein └·┘ is a floor function and N_(symb) ^(slot)is a number of symbols in one slot.
 2. The method of claim 1, whereinthe valid downlink slot criteria is based at least on a DCI processingtime.
 3. The method of claim 1, wherein N_(symb) ^(slot) is equal to 14symbols in a slot.
 4. The method of claim 1, further comprising:transmitting, by the BS and to the UE, an aperiodic reference signal(CSI-RS) in the CSI reference resource, slot n−n_(CQI_ref), wherein theCSI is determined based on the aperiodic CSI-RS, and wherein theaperiodic CSI report is generated based on the CSI.
 5. The method ofclaim 1, wherein n_(CQI_ref) is determined based on a number of symbolsZ′ related to a time for computing the CSI.
 6. The method of claim 5,wherein the valid downlink slot criteria is based at least on (i) thenumber of symbols Z′ related to the time for computing the CSI and (ii)a DCI processing time.
 7. The method of claim 5, wherein the number ofsymbols Z′ related to the time for computing the CSI is determined basedon a CSI complexity and a subcarrier spacing.
 8. The method of claim 7,wherein the number of symbols Z′ does not include a DCI processing time.9. The method of claim 5, wherein n_(CQI_ref) is determined based on thenumber of symbols Z′ related to the time for computing the CSI, andfurther based on a number of symbols in one slot.
 10. The method ofclaim 1, wherein transmitting the DCI comprises: transmitting the DCI ina slot other than the slot n in which the aperiodic CSI report is to bereceived.
 11. The method of claim 1, wherein, based on n_(CQI_ref) beingequal to zero, the aperiodic CSI report is received in a same slot astransmitting the DCI.
 12. A base station (BS) configured to receive achannel state information (CSI) report in a wireless communicationsystem, the BS comprising: a radio frequency (RF) module configured totransmit and receive radio signals; at least one processor; and at leastone computer memory operably connectable to the at least one processorand storing instructions that, when executed, cause the at least oneprocessor to perform operations comprising: transmitting, through the RFmodule to a user equipment (UE), downlink control information (DCI)related to an aperiodic CSI report that is to be received by the UE in aslot n; and receiving, through the RF module from the UE, the aperiodicCSI report in the slot n, based on a CSI reference resource being slotn−n_(CQI_ref) in a time domain, wherein the CSI reference resource inthe slot n−n_(CQI_ref) is to be used for the aperiodic CSI report,wherein n_(CQI_ref) is a smallest value greater than or equal to└Z′/N_(symb) ^(slot)┘ such that the slot n−n_(CQI_ref) satisfies a validdownlink slot criteria, and wherein └·┘ is a floor function and N_(symb)^(slot) is a number of symbols in one slot.
 13. The BS of claim 12,wherein the valid downlink slot criteria is based at least on a DCIprocessing time.
 14. The BS of claim 12, wherein N_(symb) ^(slot) isequal to 14 symbols in a slot.
 15. The BS of claim 12, wherein theoperations further comprise: transmitting, by the BS and to the UE, anaperiodic reference signal (CSI-RS) in the CSI reference resource, slotn−n_(CQI_ref), wherein the CSI is determined based on the aperiodicCSI-RS, and wherein the aperiodic CSI report is generated based on theCSI.
 16. The BS of claim 12, wherein n_(CQI_ref) is determined based ona number of symbols Z′ related to a time for computing the CSI.
 17. TheBS of claim 16, wherein the valid downlink slot criteria is based atleast on (i) the number of symbols Z′ related to the time for computingthe CSI and (ii) a DCI processing time.
 18. The BS of claim 16, whereinthe number of symbols Z′ related to the time for computing the CSI isdetermined based on a CSI complexity and a subcarrier spacing.
 19. TheBS of claim 18, wherein the number of symbols Z′ does not include a DCIprocessing time.
 20. The BS of claim 16, wherein n_(CQI_ref) isdetermined based on the number of symbols Z′ related to the time forcomputing the CSI, and further based on a number of symbols in one slot.21. The BS of claim 12, wherein transmitting the DCI comprises:transmitting the DCI in a slot other than the slot n in which theaperiodic CSI report is to be received.
 22. The BS of claim 12, wherein,based on n_(CQI_ref) being equal to zero, the aperiodic CSI report isreceived in a same slot as transmitting the DCI.